fix: comprehensive websocket and LLM model validation

- Fix original websocket format error
- Add robust model validation for all agent types
- Prevent empty model strings in LiteLLM calls
- Update Pydantic V2 compatibility (dict() -> model_dump())
- Improve error handling in workflow agents
- Add comprehensive logging and validation

Author: andersonlemesc

src/api/session_routes.py

@@ -158,7 +158,7 @@ async def get_agent_messages(
 
     processed_events = []
     for event in events:
-        event_dict = event.dict()
+        event_dict = event.model_dump()
 
         def process_dict(d):
             if isinstance(d, dict):