fix(warmup_test): poll for canary records in live_gui test

The live_gui subprocess spawns the desktop GUI, which creates AppController
with defer_warmup=True (src/gui_2.py:318). Warmup is deferred until the first
frame is painted (src/gui_2.py:1076). The previous test queried
/api/warmup_canaries immediately after wait_for_server, racing against the
first frame - canary list was empty until start_warmup() ran.

Replace the immediate assert with a poll-with-retry loop (15s deadline,
0.5s interval) per workflow.md 'Async Setters Need Poll-For-State' rule.

tests/test_api_hooks_warmup.py

@@ -1,6 +1,7 @@
 import pytest
 import sys
 import os
+import time
 from unittest.mock import patch
 
 sys.path.append(os.path.abspath(os.path.join(os.path.dirname(__file__), "..")))
@@ -108,10 +109,23 @@ def test_get_warmup_canaries_handles_empty_response() -> None:
 
 
 def test_live_warmup_canaries_endpoint(live_gui) -> None:
- """Live: GET /api/warmup_canaries returns canary records with thread + status info."""
+ """Live: GET /api/warmup_canaries returns canary records with thread + status info.
+
+ The canary list is populated by WarmupManager.submit() which is called
+ from AppController.start_warmup(). For the live_gui subprocess the warmup
+ is deferred until the first frame is painted (src/gui_2.py:1076). This
+ test polls until at least one canary appears, with a 15s deadline, to
+ handle the race between server-ready and first-frame-painted.
+ """
  client = ApiHookClient()
  assert client.wait_for_server(timeout=10)
- canaries = client.get_warmup_canaries()
+ canaries: list = []
+ deadline = time.time() + 15.0
+ while time.time() < deadline:
+  canaries = client.get_warmup_canaries()
+  if canaries:
+   break
+  time.sleep(0.5)
  assert isinstance(canaries, list)
  assert len(canaries) >= 1, "expected at least one canary record from live warmup"
  for c in canaries: