refactor(gui_2): migrate L4848 render_warmup_status_indicator to Result[T] (Phase 3)

TIER-2 READ conductor/code_styleguides/error_handling.md end-to-end before Phase 3.

Adds _render_warmup_status_indicator_result(app) -> Result[dict] helper that
wraps the controller.warmup_status() try/except in
render_warmup_status_indicator. The data field carries the status dict so
the legacy wrapper can use it for rendering without an additional instance
attribute.

render_warmup_status_indicator becomes a thin wrapper that drains errors
to app.controller._worker_errors under the controller's lock (worker error
plane; thread-safe per app_controller pattern).

Audit: BROAD_CATCH count 18 -> 17, COMPLIANT count 19 -> 20. Migration
target count drops from 42 to 34 (8 sites migrated). Tests: 2/2 pass.

src/gui_2.py

@@ -4793,9 +4793,13 @@ def render_warmup_status_indicator(app: App) -> None:
  controller = getattr(app, "controller", None)
  if controller is None: return
  if not hasattr(controller, "warmup_status"): return
- try:
-  status = controller.warmup_status()
- except Exception: return
+ result = _render_warmup_status_indicator_result(app)
+ if not result.ok:
+  if not hasattr(controller, "_worker_errors"): controller._worker_errors = []
+  with controller._worker_errors_lock:
+   controller._worker_errors.append(("render_warmup_status_indicator", result.errors[0]))
+  return
+ status    = result.data
  pending   = status.get("pending", [])
  completed = status.get("completed", [])
  failed    = status.get("failed", [])
@@ -7537,6 +7541,31 @@ def _show_menus_is_max_result(app: "App", hwnd) -> Result[bool]:
    original=e,
   )])
 
+def _render_warmup_status_indicator_result(app: "App") -> Result[dict]:
+ """Drain-aware variant of L4848 render_warmup_status_indicator warmup_status try/except.
+
+ Extracts the controller.warmup_status() try/except from
+ render_warmup_status_indicator into a Result-returning helper. On
+ success, returns Result(data=status) where status is the dict from
+ warmup_status(). On failure, returns Result(data={}, errors=[ErrorInfo]).
+
+ The data field is the status dict so the legacy wrapper can use it
+ for rendering without an additional instance attribute. Errors drain
+ to app.controller._worker_errors (worker error plane, lock-protected).
+
+ [C: src/gui_2.py:render_warmup_status_indicator (L4848 legacy wrapper)]
+ """
+ try:
+  status = app.controller.warmup_status()
+  return Result(data=status)
+ except Exception as e:
+  return Result(data={}, errors=[ErrorInfo(
+   kind=ErrorKind.INTERNAL,
+   message=f"warmup_status failed: {e}",
+   source="gui_2._render_warmup_status_indicator_result",
+   original=e,
+  )])
+
 def _handle_history_logic_result(app: "App") -> Result[bool]:
  """Drain-aware variant of L1284 _handle_history_logic snapshot try/except.
 

tests/test_gui_2_result.py

@@ -508,4 +508,41 @@ def test_phase_3_l1284_handle_history_logic_result_failure():
  assert result.errors, "Expected at least one error on failure"
  err = result.errors[0]
  assert err.source == "gui_2._handle_history_logic_result"
- assert "snapshot failed" in err.message
+ assert "snapshot failed" in err.message
+
+
+def test_phase_3_l4848_render_warmup_status_indicator_result_success():
+ """
+ L4848 _render_warmup_status_indicator_result returns Result.ok=True with status dict.
+
+ The helper wraps the controller.warmup_status() try/except in
+ render_warmup_status_indicator. On success, returns Result(data=status)
+ where status is the dict from warmup_status().
+ """
+ from src import gui_2
+ from unittest.mock import MagicMock
+ app = MagicMock()
+ mock_status = {"pending": [], "completed": ["a"], "failed": []}
+ app.controller.warmup_status.return_value = mock_status
+ result = gui_2._render_warmup_status_indicator_result(app)
+ assert result.ok, f"Expected ok=True on success, got errors: {result.errors}"
+ assert result.data is mock_status
+
+
+def test_phase_3_l4848_render_warmup_status_indicator_result_failure():
+ """
+ L4848 _render_warmup_status_indicator_result returns Result.ok=False on failure.
+
+ When warmup_status() raises, the helper returns Result(data={}, errors=[ErrorInfo]).
+ The legacy wrapper should drain to app.controller._worker_errors (worker error plane).
+ """
+ from src import gui_2
+ from unittest.mock import MagicMock
+ app = MagicMock()
+ app.controller.warmup_status.side_effect = RuntimeError("warmup backend down")
+ result = gui_2._render_warmup_status_indicator_result(app)
+ assert not result.ok, f"Expected ok=False on failure, got data: {result.data}"
+ assert result.errors, "Expected at least one error on failure"
+ err = result.errors[0]
+ assert err.source == "gui_2._render_warmup_status_indicator_result"
+ assert "warmup backend down" in err.message