feat(rag): steering notes — tune how Brain answers, stored in Postgres and injected into every system prompt

tests/unit/test_chat_gate.py

@@ -279,8 +279,19 @@ class _CannedLLM:
             yield self.answer[i : i + 12]
 
 
+class _FakeSteeringResult:
+    """Empty steering-note result (no stored notes in these unit tests)."""
+
+    def all(self) -> list[Any]:
+        return []
+
+
 class _FakeSession:
-    """Stands in for the DB session: records the QueryLog row it is given."""
+    """Stands in for the DB session: records the QueryLog row it is given.
+
+    ``scalars`` always yields no steering notes (phase 15) so the chat
+    turn's ``load_steering_notes`` call stays a no-op here.
+    """
 
     def __init__(self) -> None:
         self.added: list[Any] = []
@@ -292,6 +303,9 @@ class _FakeSession:
     def commit(self) -> None:
         self.commits += 1
 
+    def scalars(self, _stmt: Any) -> _FakeSteeringResult:
+        return _FakeSteeringResult()
+
 
 @pytest.fixture()
 def gate_env(monkeypatch: pytest.MonkeyPatch) -> Iterator[tuple[_FakeSession, _CannedLLM]]: