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>

libs/platform/src/index.ts

@@ -157,3 +157,14 @@ export {
 
 // Port configuration
 export { STATIC_PORT, SERVER_PORT, RESERVED_PORTS } from './config/ports.js';
+
+// Editor detection and launching (cross-platform)
+export {
+  commandExists,
+  clearEditorCache,
+  detectAllEditors,
+  detectDefaultEditor,
+  findEditorByCommand,
+  openInEditor,
+  openInFileManager,
+} from './editor.js';