feat(platform): add cross-platform editor utilities and refresh functionality

- Add libs/platform/src/editor.ts with cross-platform editor detection and launching
  - Handles Windows .cmd batch scripts (cursor.cmd, code.cmd, etc.)
  - Supports macOS app bundles in /Applications and ~/Applications
  - Includes caching with 5-minute TTL for performance
- Refactor open-in-editor.ts to use @automaker/platform utilities
- Add POST /api/worktree/refresh-editors endpoint to clear cache
- Add refresh button to Settings > Account for IDE selection
- Update useAvailableEditors hook with refresh() and isRefreshing

Fixes Windows issue where "Open in Editor" was falling back to Explorer
because execFile cannot run .cmd scripts without shell:true.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/ui/src/lib/http-api-client.ts

@@ -1639,6 +1639,7 @@ export class HttpApiClient implements ElectronAPI {
       this.post('/api/worktree/open-in-editor', { worktreePath, editorCommand }),
     getDefaultEditor: () => this.get('/api/worktree/default-editor'),
     getAvailableEditors: () => this.get('/api/worktree/available-editors'),
+    refreshEditors: () => this.post('/api/worktree/refresh-editors', {}),
     initGit: (projectPath: string) => this.post('/api/worktree/init-git', { projectPath }),
     startDevServer: (projectPath: string, worktreePath: string) =>
       this.post('/api/worktree/start-dev', { projectPath, worktreePath }),