fix(test): Final synchronization and stability fixes for RAG stress test

- Improved AppController.ai_status to prevent overwriting 'sending...' with 'models loaded'.
- Enhanced 	est_rag_phase4_stress.py with robust polling and increased timeout.
- Synchronized App and AppController history objects to ensure consistent view.

src/api_hook_client.py

@@ -33,6 +33,7 @@ See Also:
 """
 from __future__ import annotations
 import requests # type: ignore[import-untyped]
+import sys
 import time
 from typing import Any