Add configuration-time validation for model names using the model catalog.
Invalid models now show fuzzy suggestions. Add --force flag to skip validation.
- Add validateModelInCatalog() and validateImageModel() helpers
- Update models set, set-image, fallbacks add, image-fallbacks add
- Graceful degradation when catalog unavailable
- Add tests for validation functions
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
