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/electron.ts

@@ -1697,6 +1697,19 @@ function createMockWorktreeAPI(): WorktreeAPI {
         },
       };
     },
+    refreshEditors: async () => {
+      console.log('[Mock] Refreshing available editors');
+      return {
+        success: true,
+        result: {
+          editors: [
+            { name: 'VS Code', command: 'code' },
+            { name: 'Finder', command: 'open' },
+          ],
+          message: 'Found 2 available editors',
+        },
+      };
+    },
 
     initGit: async (projectPath: string) => {
       console.log('[Mock] Initializing git:', projectPath);