feat(agent): add redis short-term user context cache and align tests

backend/tests/unit/v1/agent/test_repository.py

@@ -0,0 +1,43 @@
+from __future__ import annotations
+
+from fastapi import HTTPException
+
+from v1.agent.repository import AgentRepository
+
+
+class _FakeSession:
+    def __init__(self) -> None:
+        self.added: list[object] = []
+
+    def add(self, obj: object) -> None:
+        self.added.append(obj)
+
+    async def flush(self) -> None:
+        return None
+
+    async def refresh(self, _obj: object) -> None:
+        return None
+
+
+async def test_create_session_for_user_creates_session_row() -> None:
+    session = _FakeSession()
+    repository = AgentRepository(session=session)  # type: ignore[arg-type]
+
+    await repository.create_session_for_user(
+        user_id="00000000-0000-0000-0000-000000000001"
+    )
+
+    session_row = session.added[0]
+    assert str(getattr(session_row, "user_id")) == "00000000-0000-0000-0000-000000000001"
+
+
+async def test_create_session_for_user_rejects_invalid_uuid() -> None:
+    session = _FakeSession()
+    repository = AgentRepository(session=session)  # type: ignore[arg-type]
+
+    try:
+        await repository.create_session_for_user(user_id="invalid-uuid")
+        raise AssertionError("expected invalid user_id")
+    except HTTPException as exc:
+        assert exc.status_code == 422
+        assert exc.detail == "Invalid user_id"