Swallow sandbox container races in the stream consumer (#552)

strix/core/agents.py

@@ -42,10 +42,14 @@ class AgentCoordinator:
         self.runtimes: dict[str, AgentRuntime] = {}
         self._lock = asyncio.Lock()
         self._snapshot_path: Path | None = None
+        self.is_shutting_down = False
 
     def set_snapshot_path(self, path: Path) -> None:
         self._snapshot_path = path
 
+    def mark_shutting_down(self) -> None:
+        self.is_shutting_down = True
+
     async def register(
         self,
         agent_id: str,