conductor(track): init test_engine_integration_20260627 (Track 1 of 3)

Spec + plan + metadata + state for the ImGui Test Engine integration.
Enables the test engine via --enable-test-engine flag, bridges it through
the existing API hooks layer (4 new /api/test_engine/* endpoints + 4 new
ApiHookClient methods), and proves the full bridge with a smoke test.

The test engine enables high-fidelity simulation of docking, window focus,
panel visibility, drag-and-drop, and keyboard input that the current Hook
API cannot express. The API hooks remain the single communication boundary;
the test engine is integrated behind it.

This is Track 1 of a 3-track campaign:
  Track 1: bridge + smoke test (this track)
  Track 2: migrate docking/focus/panel tests
  Track 3: visual regression via screenshot capture

Key risk: R1 (GIL-transfer crash) mitigated by Phase 1 Task 1.4 manual
verification checkpoint. Parallel-safe against the running tier2 taxonomy
branch and the enforcement_gap_closure track (zero file overlap).

conductor/tracks/test_engine_integration_20260627/spec.md

@@ -0,0 +1,187 @@
+# Track Specification: ImGui Test Engine Integration (Bridge via API Hooks)
+
+## Overview
+
+Integrate the Dear ImGui Test Engine (`imgui_bundle.imgui.test_engine`) into Manual Slop's test infrastructure to enable high-fidelity simulation of user interactions — docking, window focus, panel visibility, drag-and-drop, keyboard input — that the current Hook API cannot express.
+
+**The design principle:** the API hooks layer (`HookServer` on :8999 + `ApiHookClient`) remains the **single communication boundary** between the test process (pytest) and the GUI subprocess. The test engine is integrated *behind* the API hooks, not alongside them. New `/api/test_engine/*` endpoints bridge the test process to the engine's `queue_test` / `get_result_summary` API. The engine's `test_func` closures run on the engine's scenario thread (GIL-transferred by `hello_imgui`/`immapp`); they use `ctx.item_click("**/Label")`, `ctx.dock_into(src, dst, dir)`, `ctx.window_focus(ref)` etc. to post simulated input events to the GUI render thread. The existing `_pending_gui_tasks` queue and the engine's input simulation are two separate event injection paths into the same GUI thread; they compose without conflict.
+
+This is **Track 1 of 3** in the test engine campaign. Track 1 = enable the engine + build the bridge + smoke test. Track 2 (follow-up) = migrate docking/focus/panel tests. Track 3 (follow-up) = visual regression via screenshot capture.
+
+## Current State Audit (as of master `77b70226`)
+
+### Already Implemented (DO NOT re-implement)
+
+- **`imgui_bundle` v1.92.5** (pinned in `pyproject.toml:7`) ships the test engine compiled into the nanobind binary. Verified: `from imgui_bundle import imgui; imgui.test_engine.TestEngine` is a live class; `imgui.test_engine.register_test`, `imgui.test_engine.queue_test`, `imgui.test_engine.get_result_summary`, `imgui.test_engine.TestContext` with `dock_into`, `window_focus`, `item_click`, `capture_screenshot_window`, etc. are all present (verified via `dir()` enumeration — ~95 `TestContext` methods + ~35 module-level functions). The `.pyi` stub at `.venv/Lib/site-packages/imgui_bundle/imgui/test_engine.pyi` documents the full API.
+
+- **`hello_imgui.RunnerParams.use_imgui_test_engine: bool = False`** (`.venv/Lib/site-packages/imgui_bundle/hello_imgui.pyi:2969`) — the flag that enables the engine. When `True`, `hello_imgui`/`immapp` compiles the engine into the runner and provides the GIL-transfer mechanism for the scenario thread. The engine is **already compiled into the wheel** (the C++ build flag `-DHELLOIMGUI_WITH_TEST_ENGINE=ON` was set for the published wheel); the Python-side flag just activates it.
+
+- **`hello_imgui.get_imgui_test_engine()`** (`.venv/Lib/site-packages/imgui_bundle/hello_imgui.pyi:3355`) — returns the live `TestEngine` instance after `use_imgui_test_engine = True`. Verified callable.
+
+- **`RunnerCallbacks.register_tests: VoidFunction`** (`.venv/Lib/site-packages/imgui_bundle/hello_imgui.pyi:1809`) — the callback that `hello_imgui` invokes at startup to let the app register tests via `imgui.test_engine.register_test(engine, group, name)`. The demo at `.venv/Lib/site-packages/imgui_bundle/demos_python/demos_immapp/demo_testengine.py` shows the full pattern.
+
+- **`imgui_bundle.imgui.test_engine_checks.CHECK(result: bool)`** — the assertion primitive that emits pass/fail to the engine's result log with file:line traceback. Verified importable.
+
+- **The app already uses `hello_imgui.RunnerParams` + `immapp.run()`** — the exact integration path the test engine requires:
+  - `src/gui_2.py:641`: `self.runner_params = _hi.RunnerParams()`
+  - `src/gui_2.py:684-688`: `self.runner_params.callbacks.show_gui/show_menus/load_additional_fonts/setup_imgui_style/post_init` are set
+  - `src/gui_2.py:1486`: `immapp.run(app.runner_params, ...)` — the main loop entry point
+  - The GIL-transfer mechanism is built into `immapp.run` when `use_imgui_test_engine = True`; no additional threading code is needed on the Python side.
+
+- **`HookServer`** (`src/api_hooks.py:857`) — the HTTP server on `127.0.0.1:8999`, started when `--enable-test-hooks` is passed. The `do_GET` method (line 157) and `do_POST` method (line 490) use a flat `if/elif self.path == "/api/..."` dispatch. The server holds `self.app` (the `App` instance) and accesses it via `_get_app_attr(app, ...)` helpers. The `_pending_gui_tasks` queue (`app_controller.py:900`) + `_pending_gui_tasks_lock` (`app_controller.py:822`) + `_process_pending_gui_tasks()` (`app_controller.py:1844`, called per-frame from `gui_2.py:1759`) is the existing thread-safe command queue from HTTP handler thread → main render thread.
+
+- **`ApiHookClient`** (`src/api_hook_client.py`) — the Python client with retry logic, health-check polling, `wait_for_server(timeout)`, `push_event(action, payload)`, `get_value(item)`, `set_value(item, value)`, `click(item)`, `wait_for_event(event_type, timeout)`, etc. Used by all `live_gui` tests.
+
+- **`live_gui` fixture** (`tests/conftest.py:641`) — session-scoped; spawns `sloppy.py --enable-test-hooks --config=<temp>` as a subprocess; polls `http://127.0.0.1:8999/status` until ready; yields a `_LiveGuiHandle` with `.client` (an `ApiHookClient`), `.process`, `.workspace`. The fixture's subprocess args are at `conftest.py:792`: `gui_args = ["uv", "run", "python", "-u", gui_script, "--enable-test-hooks"]`.
+
+- **`sloppy.py`** (79 lines) — the entry point. CLI flags at lines 31-36: `--headless`, `--web-host`, `--web-port`, `--enable-test-hooks`, `--config`. The `else` branch at line 75 (the normal GUI mode) calls `from src.gui_2 import main; main()`.
+
+- **`AppController.test_hooks_enabled`** (`src/app_controller.py:1042`) — set via `"--enable-test-hooks" in sys.argv` or `SLOP_TEST_HOOKS=1` env var. Same pattern works for `--enable-test-engine`.
+
+### Gaps to Fill (This Track's Scope)
+
+- **GAP-1: The test engine is not enabled.** `runner_params.use_imgui_test_engine` is never set to `True`. No `callbacks.register_tests` callback exists. The engine's scenario thread + GIL-transfer mechanism are dormant.
+
+- **GAP-2: No `/api/test_engine/*` bridge endpoints.** The `HookServer` has no way for the test process to queue a test, poll results, or abort a running test. The test engine API (`queue_test`, `get_result_summary`, `is_test_queue_empty`, `abort_current_test`) is only accessible from inside the GUI process — not from the HTTP boundary.
+
+- **GAP-3: No `ApiHookClient` methods for test engine operations.** The client has `click`, `set_value`, `push_event`, `wait_for_event` — but no `queue_test`, `wait_for_test_results`, `get_test_results`.
+
+- **GAP-4: `live_gui` fixture doesn't pass `--enable-test-engine`.** The subprocess at `conftest.py:792` only passes `--enable-test-hooks`. Without the engine flag, the engine won't activate even after GAP-1 is fixed.
+
+- **GAP-5: No smoke test proving the end-to-end threading model works.** The test engine's scenario thread + GIL transfer is the highest-risk piece. A minimal smoke test (register a trivial test that clicks a known button + asserts a state change, queue it via the API, poll for results, assert pass) is needed to prove the bridge works before Track 2 migrates real tests.
+
+### Architecture: Why the API hooks + test engine compose
+
+```
+pytest test process
+  └── ApiHookClient (HTTP :8999)          ← single communication boundary (KEPT)
+       └── HookServer.do_POST             ← new /api/test_engine/* endpoints
+            └── imgui.test_engine.queue_test(engine, test)  ← schedules on engine
+                 └── TestContext.test_func(ctx)  ← runs on engine scenario thread
+                      └── ctx.item_click("**/Label")  ← posts simulated input to GUI thread
+                           └── GUI render thread processes the simulated event
+                                └── _process_pending_gui_tasks() still runs per-frame
+                                     (existing queue; unaffected; two separate injection paths)
+```
+
+The test engine's `test_func` runs on its own thread (the scenario thread). The `ctx.*` primitives post simulated input events to the ImGui input queue on the GUI render thread. This is the same destination as real user input and the same destination as `_pending_gui_tasks` — but a different injection mechanism. The two paths are independent; they don't share state, locks, or queues. The test engine doesn't touch `_pending_gui_tasks` and vice versa.
+
+The GIL-transfer caveat (documented at the top of `test_engine.pyi`) is handled by `hello_imgui`/`immapp` when `use_imgui_test_engine = True` — the C++ layer transfers the GIL between the main thread and the scenario thread. No additional Python-side threading code is needed. The `test_func` callback runs with the GIL held; it can safely call `ctx.*` primitives (which are C++ nanobind calls that release the GIL during the simulated input wait).
+
+## Goals
+
+- **G1.** `sloppy.py` accepts `--enable-test-engine` CLI flag; when set, `App.run()` sets `runner_params.use_imgui_test_engine = True` + assigns `runner_params.callbacks.register_tests` to a method that registers tests.
+
+- **G2.** `App` has a `_register_imgui_tests(self)` method (called by `hello_imgui` at startup via the `register_tests` callback) that registers at least one smoke test ("Smoke Tests", "Click Increment Button") via `imgui.test_engine.register_test(engine, group, name)`. The smoke test's `test_func(ctx)` calls `ctx.set_ref("...")` + `ctx.item_click("**/...")` + `CHECK(...)`.
+
+- **G3.** `HookServer` (in `src/api_hooks.py`) has 4 new endpoints:
+  - `POST /api/test_engine/queue` — body `{"group": "...", "name": "..."}`; finds the test by group+name via `imgui.test_engine.find_test_by_name(engine, group, name)`; calls `queue_test(engine, test)`; responds `{"status": "queued"}`.
+  - `GET /api/test_engine/status` — calls `is_test_queue_empty(engine)`; responds `{"queue_empty": true/false}`.
+  - `GET /api/test_engine/results` — calls `get_result_summary(engine, out_results)`; responds `{"count_tested": N, "count_success": N, "count_in_queue": N}`.
+  - `POST /api/test_engine/abort` — calls `abort_current_test(engine)`; responds `{"status": "aborted"}`.
+
+- **G4.** `ApiHookClient` (in `src/api_hook_client.py`) has 4 new methods:
+  - `queue_test(group: str, name: str) -> dict` — POST to `/api/test_engine/queue`.
+  - `get_test_status() -> dict` — GET `/api/test_engine/status`.
+  - `get_test_results() -> dict` — GET `/api/test_engine/results`.
+  - `wait_for_test_results(timeout: float = 30.0) -> dict` — polls `get_test_status()` until `queue_empty == True` or timeout; then returns `get_test_results()`.
+
+- **G5.** The `live_gui` fixture passes `--enable-test-engine` in addition to `--enable-test-hooks` in the subprocess args (`conftest.py:792`). The engine activates on every `live_gui` test run.
+
+- **G6.** A smoke test in `tests/test_test_engine_smoke.py` that:
+  1. Uses the `live_gui` fixture.
+  2. Queues the smoke test via `client.queue_test("Smoke Tests", "Click Increment Button")`.
+  3. Polls via `client.wait_for_test_results(timeout=30)`.
+  4. Asserts `results["count_success"] >= 1` and `results["count_tested"] >= 1`.
+  This proves the full bridge works: pytest → HTTP → HookServer → engine → scenario thread → `ctx.item_click` → GUI thread → state change → `CHECK` → result log → `get_result_summary` → HTTP → pytest assert.
+
+- **G7.** End-of-track report at `docs/reports/TRACK_COMPLETION_test_engine_integration_20260627.md` documenting: what shipped, the threading model verification, any GIL-transfer issues encountered, and the handoff to Track 2 (docking test migration).
+
+## Functional Requirements
+
+### FR1: `--enable-test-engine` CLI flag
+
+- `sloppy.py`: add `parser.add_argument("--enable-test-engine", action="store_true", help="Enable the Dear ImGui Test Engine for automated UI testing")` alongside the existing `--enable-test-hooks` flag (line 35).
+- `src/app_controller.py`: add `self.test_engine_enabled: bool = ("--enable-test-engine" in sys.argv)` near line 1042 (same pattern as `test_hooks_enabled`).
+- `src/gui_2.py` `App.run()` (line 619): between the `RunnerParams()` construction (line 641) and the `callbacks.show_gui = ...` assignments (line 684), add:
+  ```python
+  if getattr(self.controller, "test_engine_enabled", False):
+   self.runner_params.use_imgui_test_engine = True
+   self.runner_params.callbacks.register_tests = self._register_imgui_tests
+  ```
+  This is guarded by the flag so normal runs are unaffected.
+
+### FR2: `App._register_imgui_tests(self)` method
+
+- New method on `App` in `src/gui_2.py` (near the other callback registrations, ~line 700):
+  ```python
+  def _register_imgui_tests(self) -> None:
+   """Called by hello_imgui at startup to register ImGui Test Engine tests.
+   Reads the live engine via hello_imgui.get_imgui_test_engine().
+   [C: src/gui_2.py:App.run (via callbacks.register_tests)]
+   """
+   from imgui_bundle import hello_imgui
+   from imgui_bundle.imgui import test_engine
+   engine = hello_imgui.get_imgui_test_engine()
+   # Smoke test: click a known button and verify state change
+   test = test_engine.register_test(engine, "Smoke Tests", "Click Increment Button")
+   def smoke_func(ctx) -> None:
+    from imgui_bundle.imgui.test_engine_checks import CHECK
+    ctx.set_ref("...")  # TODO: set to a known window
+    ctx.item_click("**/...")  # TODO: click a known button
+    CHECK(True)  # TODO: verify state change
+   test.test_func = smoke_func
+  ```
+  The exact button + state to click + verify is determined during implementation by inspecting the running GUI's item tree (use `ctx.window_info` / `imgui.show_id_stack_tool_window` to find labels). The smoke test should click something harmless (e.g., a tab switch, a checkbox toggle) and verify the state changed.
+
+### FR3: `/api/test_engine/*` endpoints in `HookServer`
+
+- In `src/api_hooks.py` `do_POST` (line 490): add 2 new `elif` branches for `POST /api/test_engine/queue` and `POST /api/test_engine/abort`.
+- In `src/api_hooks.py` `do_GET` (line 157): add 2 new `elif` branches for `GET /api/test_engine/status` and `GET /api/test_engine/results`.
+- All 4 endpoints guard on `test_engine_enabled` — if the engine is not active, respond `{"error": "test engine not enabled", "enabled": false}` with HTTP 503.
+- The engine instance is obtained via `hello_imgui.get_imgui_test_engine()` inside the handler (lazy import; the handler runs on the HTTP thread, but `get_imgui_test_engine()` is a C++ accessor that returns a pointer — safe to call from any thread).
+
+### FR4: `ApiHookClient` methods
+
+- In `src/api_hook_client.py`: add 4 methods per G4. Follow the existing method pattern (e.g., `get_status`, `push_event`): construct the URL, `requests.post/get`, retry on connection error, parse JSON, return the dict.
+
+### FR5: `live_gui` fixture update
+
+- In `tests/conftest.py:792`: change `gui_args` to include `"--enable-test-engine"` when the fixture spawns the subprocess. The flag flows through to `AppController.test_engine_enabled` → `App.run()` → `runner_params.use_imgui_test_engine = True`.
+
+### FR6: Smoke test
+
+- `tests/test_test_engine_smoke.py` (NEW) — 2-3 tests:
+  - `test_engine_enabled`: `client.get_value("test_engine_enabled")` returns True (or verify via a new gettable field).
+  - `test_queue_and_run_smoke_test`: queue the smoke test, poll for results, assert success.
+  - `test_engine_results_shape`: `get_test_results()` returns the expected dict shape.
+
+## Non-Functional Requirements
+
+- **1-space indentation** for all Python code.
+- **No comments in body** per AGENTS.md.
+- **CRLF line endings** preserved.
+- **Atomic per-task commits.**
+- **Thread safety:** the `test_func` runs on the engine scenario thread. It must NOT directly mutate `App` or `AppController` state — it must use `ctx.*` primitives (which post simulated input to the GUI thread). Reading state via `hello_imgui.get_imgui_test_engine()` or engine queries (`ctx.item_info`, `ctx.window_info`) is safe. The `CHECK()` assertion runs on the scenario thread but only writes to the engine's result log (thread-safe C++ structure).
+- **No `live_gui` regression:** the `--enable-test-engine` flag must not affect normal GUI behavior when `live_gui` tests are NOT using the engine. The engine's scenario thread is idle when no tests are queued. The `show_test_engine_windows` panel is NOT shown by default (only via explicit call).
+- **Performance:** the engine adds a per-frame overhead when active. The `fps_idling` settings in `runner_params` remain unchanged. The engine's overhead is sub-millisecond per frame when no tests are running.
+
+## Architecture Reference
+
+- **`docs/guide_testing.md`** — the `live_gui` fixture, the structural testing contract, the Puppeteer pattern.
+- **`docs/guide_api_hooks.md`** — the Hook API surface, the `/api/ask` protocol, the `ApiHookClient` method reference.
+- **`docs/guide_gui_2.md`** — the `App` class lifecycle, the `runner_params` construction, the `callbacks` system.
+- **`.venv/Lib/site-packages/imgui_bundle/demos_python/demos_immapp/demo_testengine.py`** — the canonical demo for the test engine integration pattern (register_tests callback + test_func closures + CHECK).
+- **`.venv/Lib/site-packages/imgui_bundle/imgui/test_engine.pyi`** — the full API stub (2644 lines). Key sections: `TestContext` methods (lines 1445-2096), module-level functions (lines 433-500, 2639+), `TestEngineResultSummary` (3 fields: count_tested, count_success, count_in_queue).
+- **`.venv/Lib/site-packages/imgui_bundle/imgui/test_engine_checks.py`** — the `CHECK(result: bool)` assertion primitive.
+- **`conductor/workflow.md`** "Live_gui Test Fragility" + "Async Setters Need Poll-For-State" — the existing patterns for `live_gui` tests; the test engine's `wait_for_test_results` replaces `time.sleep` + `get_value` polling with a single engine-side poll.
+
+## Out of Scope
+
+- **Migrating existing `live_gui` tests to the test engine.** That's Track 2 (`test_engine_docking_tests_<date>`). This track only builds the bridge + proves it works with 1 smoke test.
+- **Visual regression via screenshot capture.** That's Track 3 (`test_engine_capture_regression_<date>`). The `ctx.capture_screenshot_window` API is available but not wired in this track.
+- **Headless test execution (no GUI window).** The test engine requires a live GLFW window (the scenario thread drives the actual ImGui render loop). Headless mode is a future research item, not this track.
+- **The test engine's interactive UI panel (`show_test_engine_windows`).** Not shown by default. Can be added as a debug toggle in a follow-up.
+- **Test engine license audit.** Per the stub: "free for individuals, educational, open-source, and small businesses. Paid for larger businesses." This project is personal-use; no audit needed. Flagged for awareness only.
+- **CI wiring of the test engine.** The `live_gui` fixture already runs in CI via the batched runner. The `--enable-test-engine` flag is additive. No CI config changes needed.
+- **Touching `src/models.py` or any taxonomy files.** Zero overlap with the running `tier2/post_module_taxonomy_de_cruft_20260627` branch or the `enforcement_gap_closure_20260627` track.