refactor(tests): per-model fakes, FakeMCP and session mocks come from tests/helpers (#2825, milestone 296 area 1, batch 2)

Second pass over the tests/ ledger after bbee0d0. fake_record(**attrs) is the
one MagicMock-with-real-attributes builder (to_dict mirrors them; the
note-2109 hazard documented once); fake_note/fake_task/fake_snippet/
fake_project/fake_milestone/fake_system/fake_rulebook/fake_topic/fake_rule
carry each model's ordinary defaults on top of it, replacing 14 per-file
factories (two rulebook trios in tool-vs-service wordings, _fake_task, _fake_ms,
_fake_project, _plan_note, _fake_snippet, two _snippet adapters now one-liners
over fake_snippet). FakeMCP replaces the five closure-over-a-list registrar
fakes (+ _Recorder); loc() and design_token_stub() replace the paired _loc /
_token / _T stand-ins; every hand-built async_session mock (9 helper defs and
14 inline copies) now starts from make_mock_session(). Call sites rewritten by
AST with each file's former defaults made explicit, so behaviour is unchanged.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/test_notes_description_field.py

@@ -5,17 +5,16 @@ from `body` which (post-Task-as-Durable-Record) becomes the LLM-maintained
 consolidation summary.
 """
 from unittest.mock import AsyncMock, MagicMock, patch
+from tests.helpers import make_mock_session
 
 
 def _mock_session_for_update(mock_note):
-    mock_session = AsyncMock()
+    mock_session = make_mock_session()
     mock_result = MagicMock()
     mock_result.scalars.return_value.first.return_value = mock_note
     mock_session.execute = AsyncMock(return_value=mock_result)
     mock_session.commit = AsyncMock()
     mock_session.refresh = AsyncMock()
-    mock_session.__aenter__ = AsyncMock(return_value=mock_session)
-    mock_session.__aexit__ = AsyncMock(return_value=False)
     return mock_session
 
 
@@ -56,12 +55,10 @@ async def test_create_note_forwards_description_to_model():
             for k, v in kw.items():
                 setattr(self, k, v)
 
-    mock_session = AsyncMock()
+    mock_session = make_mock_session()
     mock_session.add = MagicMock()
     mock_session.commit = AsyncMock()
     mock_session.refresh = AsyncMock()
-    mock_session.__aenter__ = AsyncMock(return_value=mock_session)
-    mock_session.__aexit__ = AsyncMock(return_value=False)
 
     with patch(
         "scribe.services.notes.async_session", return_value=mock_session