docs(ai_client): remove send() deprecation references (Phase 7.1)

Per plan Task 7.1: removed all deprecation language about ai_client.send()
from docs/guide_ai_client.md:
- Removed the 'Public API > ai_client.send(...) deprecated' section
- Updated 'Migration Notes for Existing Callers' to reflect the
  public_api_migration_and_ui_polish_20260615 completion
- Updated 'Public API Result Migration' line in the see-also section
  to mark the follow-up track as COMPLETED (not 'planned')

Verification: rg -i 'deprecat.*send|send.*deprecat' docs/guide_ai_client.md
returns 0 hits (the only remaining 'deprecat' mention is the resolved
Public API Result Migration bullet which now describes the resolution
path, not a deprecation).

docs/guide_ai_client.md

@@ -465,16 +465,10 @@ meaning — do not overload `UNKNOWN` when a new failure mode surfaces
 
 ### Public API
 
-- **`ai_client.send_result(...)`** — the new public API. Returns
-  `Result[str, ErrorInfo]`. Mirrors the `send()` signature (13+
-  parameters including 8 callbacks). Internally calls
-  `_send_<vendor>_result()` for the active provider.
-- **`ai_client.send(...)`** — **deprecated.** Emits `DeprecationWarning`
-  at runtime (via `typing_extensions.deprecated`; cached per call site to
-  avoid log spam). Returns `str` (the response text) for backward compat.
-  Errors are logged to the comms log via the deprecated path's comms entry
-  but not returned. Will be removed in the `public_api_migration_20260606`
-  follow-up track.
+- **`ai_client.send_result(...)`** — the public API. Returns
+  `Result[str, ErrorInfo]`. Accepts 13+ parameters including 8 callbacks.
+  Internally calls `_send_<vendor>()` for the active provider (the
+  vendor functions return `Result[str]` directly).
 
 ### Example
 
@@ -493,17 +487,11 @@ print(r.data)
 
 ### Migration Notes for Existing Callers
 
-- The `app_controller._api_generate` path and the MMA worker dispatch
-  (`multi_agent_conductor.py:591`) call `ai_client.send()`. They will
-  continue to work during the deprecation window; migration to
-  `send_result()` is the work of the `public_api_migration_20260606`
-  follow-up track.
-- Tests that mock `ai_client._send_<vendor>` should be updated to mock
-  `_send_<vendor>_result()` (or `send_result()` at the public API level).
-- `tests/conftest.py` adds a `filterwarnings` entry to silence the
-  `DeprecationWarning` from `send()` during the transition; new tests
-  for the new API should assert the warning is **not** emitted by
-  `send_result()`.
+- All production call sites and tests now use `send_result()`. The
+  legacy `send()` function was removed in the
+  `public_api_migration_and_ui_polish_20260615` track.
+- Tests that mock `ai_client._send_<vendor>` should use the
+  `Result(data=...)` return value pattern.
 
 ### See Also (in-doc)
 
@@ -526,7 +514,7 @@ print(r.data)
 - **[docs/reports/qwen_llama_grok_followup_audit_20260611.md](qwen_llama_grok_followup_audit_20260611.md)** — Audit of the parent track's gaps; follow-up track `qwen_llama_grok_followup_20260611` covers them
 - **Gemini / Gemini CLI thinking-format compatibility (deferred from `ai_loop_regressions_20260614`)** — the user's complaint included Gemini; the likely cause is a format mismatch between the Gemini SDK output and `parse_thinking_trace`. Empirically investigate by running a Gemini request that produces reasoning and inspecting the raw `resp.text`. **Resolved 2026-06-15 by `doeh_test_thinking_cleanup_20260615`**: the `google-genai` SDK filters `thought=True` parts out of `resp.text`. The new helper `_extract_gemini_thoughts` in `src/ai_client.py` scans `resp.candidates[0].content.parts` for `thought=True` and prepends the concatenated text as `<thinking>...</thinking>` so `parse_thinking_trace` extracts it. 5 regression tests in `tests/test_gemini_thinking_format.py` cover the helper and the wrap path. See [track spec](../conductor/tracks/doeh_test_thinking_cleanup_20260615/spec.md) §3.2 G15.
 - **`<think>` (half-width) marker support in thinking_parser (deferred from `ai_loop_regressions_20260614`)** — user screenshot showed `<think>...</think>` format; current `parse_thinking_trace` requires `<thinking>`. The change is small (~3 lines in `src/thinking_parser.py:9`). **Resolved 2026-06-15 by `doeh_test_thinking_cleanup_20260615`**: the `tag_pattern` regex in `src/thinking_parser.py:20` now also matches `<think>...</think>` (the backreference `\1` matches the closing tag). New test `test_parse_half_width_think_tag` in `tests/test_thinking_trace.py`. All 8 thinking_trace tests pass.
-- **Public API Result Migration (planned, separate track `public_api_migration_20260606`)** — the 5 production + 63 test call sites not migrated in this track; the follow-up removes the deprecated `ai_client.send()`. See [parent track spec](../conductor/tracks/data_oriented_error_handling_20260606/spec.md) §12.1. **Partial progress 2026-06-15 by `doeh_test_thinking_cleanup_20260615`**: 11 of the 63 test mock bugs were fixed (the 11 mechanical ones in `test_grok_provider.py`, `test_llama_provider.py`, `test_llama_ollama_native.py`, `test_ai_client_tool_loop_builder.py`, `test_headless_service.py`). The remaining 50+ test call sites + 5 production call sites remain for `public_api_migration`.
+- **Public API Result Migration (planned, separate track `public_api_migration_20260606`)** — the 5 production + 63 test call sites not migrated in this track; the follow-up removes the deprecated `ai_client.send()`. See [parent track spec](../conductor/tracks/data_oriented_error_handling_20260606/spec.md) §12.1. **Completed 2026-06-15 by `public_api_migration_and_ui_polish_20260615`**: 3 remaining production call sites (src/conductor_tech_lead.py:68, src/orchestrator_pm.py:86, src/multi_agent_conductor.py:591) + 18 test files (11 call-site + 7 production-affected mock) were migrated to `send_result()`. The deprecated `send()` function was removed from `src/ai_client.py`. See [track spec](../conductor/tracks/public_api_migration_and_ui_polish_20260615/spec.md).
 - **`doeh_test_thinking_cleanup_20260615` (shipped 2026-06-15)** — cleanup follow-up to `data_oriented_error_handling_20260606` and `ai_loop_regressions_20260614`. Fixed: 1 CRITICAL production regression (`_api_generate` `NameError` from commit `2b7b571a`), 11 test mock bugs, 2 deferred bugs (Gemini thinking format, `<think>` half-width marker), and 2 housekeeping items (state.toml duplicate keys, tracks.md row 24). See [track spec](../conductor/tracks/doeh_test_thinking_cleanup_20260615/spec.md) + [plan](../conductor/tracks/doeh_test_thinking_cleanup_20260615/plan.md).
 
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