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_integration_snippet_locations.py

@@ -31,14 +31,11 @@ from scribe.services.snippets import (
     list_snippets,
     snippet_fields,
 )
+from tests.helpers import loc
 
 pytestmark = [pytest.mark.integration, pytest.mark.usefixtures("_dispose_engine")]
 
 
-def _loc(repo="", path="", symbol=""):
-    return {"repo": repo, "path": path, "symbol": symbol}
-
-
 @pytest_asyncio.fixture
 async def seeded():
     """A user with four snippets covering the cases the filter has to separate.
@@ -60,13 +57,13 @@ async def seeded():
                 data=compose_data(name=name, language="python", locations=locations),
             )
 
-        nested = _snippet("nested", [_loc("Scribe", "frontend/src/lib/x.ts", "helper")])
-        sibling = _snippet("sibling", [_loc("Scribe", "frontend/srcmap.ts", "other")])
+        nested = _snippet("nested", [loc(repo="Scribe", path="frontend/src/lib/x.ts", symbol="helper")])
+        sibling = _snippet("sibling", [loc(repo="Scribe", path="frontend/srcmap.ts", symbol="other")])
         # Two locations, deliberately crossed: repo Scribe at src/a.py and repo
         # Portal at src/b.py. repo=Scribe + path=src/b.py must NOT match it.
         multi = _snippet(
             "multi",
-            [_loc("Scribe", "src/a.py", "alpha"), _loc("Portal", "src/b.py", "beta")],
+            [loc(repo="Scribe", path="src/a.py", symbol="alpha"), loc(repo="Portal", path="src/b.py", symbol="beta")],
         )
         # No structured location at all — must never satisfy a location filter,
         # and must not error the query either.
@@ -242,7 +239,7 @@ async def test_backfill_makes_a_pre_0070_snippet_findable_by_location(seeded):
     defaults to none_as_null=False) — a different state, covered by the next test.
     """
     user_id, _ids = seeded
-    locations = [_loc("Legacy", "old/path/y.py", "legacy_helper")]
+    locations = [loc(repo="Legacy", path="old/path/y.py", symbol="legacy_helper")]
     async with async_session() as s:
         old = Note(
             user_id=user_id,