fix(tests): update consumer sites to import Pydantic proxies from src.api_hooks

Per Tier 1 review of post_module_taxonomy_de_cruft_20260627 (the
commit 6b0668f1 + aa80bc13 work moved GenerateRequest +
ConfirmRequest to src.api_hooks.py and removed the lazy __getattr__
proxy for them in src/models.py). The TRACK_COMPLETION's test
verification missed the 5 sites in test_models_no_top_level_pydantic.py
+ 1 site in test_project_switch_persona_preset.py that still did
'from src.models import GenerateRequest/ConfirmRequest' after the
move.

This commit:
 - tests/test_models_no_top_level_pydantic.py: 5 sites updated
   (lines 49, 60, 74, 88, 99) from
     'from src.models import GenerateRequest/ConfirmRequest'
   to
     'from src.api_hooks import GenerateRequest/ConfirmRequest'
 - tests/test_project_switch_persona_preset.py: 1 site updated
   (line 299) same change

After this commit:
 - All 'from src.models import GenerateRequest/ConfirmRequest'
   references in tests/ are gone (vc10 confirmed)
 - tests/test_models_no_top_level_pydantic.py tests are now functional
   (they error only on the live_gui session fixture setup, which is
   a pre-existing test infrastructure issue documented in the
   TRACK_COMPLETION's Known Issues section; the test bodies themselves
   are correct and will run once the live_gui fixture is fixed)
 - The 2 test files now import from the new home of the Pydantic
   proxies (src.api_hooks)

A direct subprocess verification (bypassing the live_gui fixture)
confirms the imports work:
 uv run python scripts/tier2/artifacts/post_module_taxonomy_de_cruft_20260627/verify_pydantic_test.py
 # Output:
 #   pydantic in sys.modules: False
 #   src.models imported OK
 #   GenerateRequest: <class 'src.api_hooks.GenerateRequest'>
 #   ConfirmRequest: <class 'src.api_hooks.ConfirmRequest'>

tests/test_project_switch_persona_preset.py

@@ -296,7 +296,7 @@ def test_api_generate_blocked_while_stale(tmp_path, monkeypatch):
     assert ctrl.is_project_stale()
     from fastapi import HTTPException
     from src.app_controller import _api_generate
-    from src.models import GenerateRequest
+    from src.api_hooks import GenerateRequest
     req = GenerateRequest(prompt="hello")
     with pytest.raises(HTTPException) as exc_info:
         _api_generate(ctrl, req)