- Add server-side file service with list, read, and write operations
- Add file API routes with comprehensive tests
- Create useFileBrowser and useFileEditor hooks for state management
- Add FileBrowser, FileEditor, and FileBrowserModal components
- Integrate Files tab into TaskDetailModal for task worktree browsing
- Add CodeMirror 6 dependencies for syntax highlighting
- Include file browser styles with light/dark theme support
- Add section expansion state management with localStorage persistence
- Update section headers with chevron toggle controls
- Implement conditional task row rendering based on section state
- Add Expand All / Collapse All toolbar controls
- Add CSS styles for chevron rotation animation and section headers
- Add comprehensive tests for collapsible section behavior
