Implement runtime agent loop and container hygiene

app/memory/repository.py

@@ -95,6 +95,21 @@ class Repository:
         result = await self.session.execute(stmt)
         return list(result.scalars().all())
 
+    async def get_messages_since(
+        self, session_id: str, since: datetime
+    ) -> list[ChatMessage]:
+        """Get messages recorded since a specific timestamp."""
+        stmt = (
+            select(ChatMessage)
+            .where(
+                ChatMessage.session_id == session_id,
+                ChatMessage.timestamp >= since,
+            )
+            .order_by(ChatMessage.timestamp.desc())
+        )
+        result = await self.session.execute(stmt)
+        return list(result.scalars().all())
+
     # Agent Action operations
 
     async def record_action(