Add auto-disable feature for models that fail 3 times in --auto mode

- Add auto_disable.json to track failure counts and disabled status
- Models that fail 3 times in auto mode are automatically disabled
- Disabled models are skipped during auto model selection
- Manual selection of a disabled model re-enables it for auto mode
- Model list now shows 'Auto' column with status (Yes, OFF, or X/3)
- Disabled models shown with 🚫 indicator in model list
- New functions: load_auto_disable_data(), save_auto_disable_data(),
  record_model_failure(), is_model_disabled(), re_enable_model(),
  get_model_fail_count()