Enhance the todo tracker sidebar panel with:
- Group todos by heading from the source file
- Display nested (indented) todos as a tree
- Drag-and-drop to reorder todos within/across heading groups
- Keyboard navigation (arrow keys, Enter to open, M to move, toggle hotkey)
- Right-click context menu replacing the ellipsis button
- Proper focus management (no focus stealing on refresh)
- Platform-aware Obsidian hotkey matching for toggle checkbox
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
