Add model selection feature with UI controls

- Add model selector dropdown in chat interface (Opus, Sonnet, Default)
- Model preference persists across sessions using workspace state
- Add model validation to prevent invalid selections
- Display confirmation messages when switching models
- Update Claude command to include --model flag when specific model selected
- Reorganize input controls layout for better UX
- Update documentation in README.md and CHANGELOG.md

package.json

@@ -2,7 +2,7 @@
   "name": "claude-code-chat",
   "displayName": "Claude Code Chat",
   "description": "Beautiful Claude Code Chat Interface for VS Code",
-  "version": "0.0.8",
+  "version": "0.0.9",
   "publisher": "AndrePimenta",
   "author": "Andre Pimenta",
   "repository": {