fix: add warning log when response ID cannot be normalized

Log a warning when a string response ID cannot be converted to an
integer, as this means the response will never match any pending
request (since the client always sends integer IDs).

Author: claude

src/mcp/shared/session.py

@@ -473,7 +473,7 @@ def _normalize_request_id(self, response_id: RequestId) -> RequestId:
             try:
                 return int(response_id)
             except ValueError:
-                pass
+                logging.warning(f"Response ID {response_id!r} cannot be normalized to match pending requests")
         return response_id
 
     async def _handle_response(self, message: SessionMessage) -> None: