Fix MCP session handling - allow requests without session ID

app.py

@@ -373,18 +373,18 @@ async def mcp_post_handler(request: Request):
                 }
             }
         
-        # Handle other requests with session
-        if not session_id or session_id not in sessions:
+        # Handle other requests - allow without session for MCP compatibility
+        if session_id and session_id not in sessions:
             return {
                 "jsonrpc": "2.0",
                 "error": {
                     "code": -32000,
-                    "message": "Bad Request: No valid session ID provided"
+                    "message": "Bad Request: Invalid session ID provided"
                 },
                 "id": body.get("id")
             }
         
-        session = sessions[session_id]
+        session = sessions.get(session_id) if session_id else None
         method = body.get("method")
         params = body.get("params", {})
         request_id = body.get("id")