fix: Use chatbot_state instead of chatbot_value

- Change from chatbot.chatbot_value to chatbot.chatbot_state
- Fixes AttributeError on Hugging Face Spaces deployment
- chatbot_state is the correct attribute in Gradio ChatInterface

Resolves runtime error:
AttributeError: 'ChatInterface' object has no attribute 'chatbot_value'

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

app.py

@@ -251,7 +251,7 @@ with gr.Blocks(
     model_dropdown.change(
         fn=on_model_change,
         inputs=[model_dropdown],
-        outputs=[chatbot.chatbot_value, model_warning, model_warning],
+        outputs=[chatbot.chatbot_state, model_warning, model_warning],
     )
 
     gr.Markdown(