fix: remove leftover sys.stderr debug log causing NameError

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

gateway/assistant.py

@@ -1511,7 +1511,6 @@ def handle_assistant(handler, body, user):
 
     if domain == "fitness":
         fitness_state = unified_state.get("fitnessState") or {}
-        print(f"[Dispatcher] fitnessState={json.dumps(fitness_state)[:300]}", file=sys.stderr)
         inner_body = json.dumps({
             "action": action,
             "messages": messages_raw,