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_api_keys.py

@@ -13,6 +13,7 @@ from scribe.services.api_keys import (
     revoke_api_key,
     lookup_key,
 )
+from tests.helpers import make_mock_session
 
 
 def test_generate_key_format():
@@ -45,9 +46,7 @@ async def test_create_api_key_returns_full_key():
     mock_key_obj.to_dict.return_value = {"id": 1, "name": "test", "scope": "read", "key_prefix": "fmcp_xxx"}
 
     with patch("scribe.services.api_keys.async_session") as mock_session_ctx:
-        mock_session = AsyncMock()
-        mock_session.__aenter__ = AsyncMock(return_value=mock_session)
-        mock_session.__aexit__ = AsyncMock(return_value=False)
+        mock_session = make_mock_session()
         mock_session.add = MagicMock()
         mock_session.commit = AsyncMock()
         mock_session.refresh = AsyncMock(side_effect=lambda obj: None)
@@ -67,9 +66,7 @@ async def test_create_api_key_returns_full_key():
 @pytest.mark.asyncio
 async def test_lookup_key_returns_none_for_unknown():
     with patch("scribe.services.api_keys.async_session") as mock_session_ctx:
-        mock_session = AsyncMock()
-        mock_session.__aenter__ = AsyncMock(return_value=mock_session)
-        mock_session.__aexit__ = AsyncMock(return_value=False)
+        mock_session = make_mock_session()
         mock_result = MagicMock()
         mock_result.scalars.return_value.first.return_value = None
         mock_session.execute = AsyncMock(return_value=mock_result)