- Use truncateToWidth instead of substring in user-message-selector.ts
- Fix truncateToWidth to use Intl.Segmenter for proper grapheme handling
- Add tests for Unicode truncation behavior
- Add /branch slash command to create conversation branches
- New UserMessageSelectorComponent shows all user messages chronologically
- Selecting a message creates new session with messages before selection
- Selected message is placed in editor for modification/resubmission
- SessionManager.createBranchedSession() creates new session files
- Updated README.md and CHANGELOG.md with /branch documentation