Add comprehensive editor detection and selection system that allows users
to configure their preferred IDE for opening branches and worktrees.
## Server-side Changes
- Add `/api/worktree/available-editors` endpoint to detect installed editors
- Support detection via CLI commands (cursor, code, zed, subl, etc.)
- Support detection via macOS app bundles in /Applications and ~/Applications
- Detect editors: Cursor, VS Code, Zed, Sublime Text, Windsurf, Trae,
Rider, WebStorm, Xcode, Android Studio, Antigravity, and file managers
## UI Changes
### Editor Icons
- Add new `editor-icons.tsx` with SVG icons for all supported editors
- Icons: Cursor, VS Code, Zed, Sublime Text, Windsurf, Trae, Rider,
WebStorm, Xcode, Android Studio, Antigravity, Finder
- `getEditorIcon()` helper maps editor commands to appropriate icons
### Default IDE Setting
- Add "Default IDE" selector in Settings > Account section
- Options: Auto-detect (Cursor > VS Code > first available) or explicit choice
- Setting persists via `defaultEditorCommand` in global settings
### Worktree Dropdown Improvements
- Implement split-button UX for "Open In" action
- Click main area: opens directly in default IDE (single click)
- Click chevron: shows submenu with other editors + Copy Path
- Each editor shows with its branded icon
## Type & Store Changes
- Add `defaultEditorCommand: string | null` to GlobalSettings
- Add to app-store with `setDefaultEditorCommand` action
- Add to SETTINGS_FIELDS_TO_SYNC for persistence
- Add `useAvailableEditors` hook for fetching detected editors
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
