feat(sync-ui): defer app quit until async cleanup resolves

- check-host participates in active-run coordination and can be cancelled
- shutdown() cancels and awaits the active launcher run on quit
- onWillQuit calls preventDefault and re-triggers quit once cleanup settles
- Snapshot mode awaits tracker quiescent before writing output
- Auto-scheduler catches synchronous triggerHostSync failures
- SCP endpoint accepts Windows absolute paths; cmd.exe rejects % in quoted values
- runAppCommand unified (inherit vs pipe stdio) in launcher/mpv.ts
- Docs: add --check, --json, --ui, --sync-cli, --make-temp/--remove-temp examples

src/main/runtime/startup-lifecycle-main-deps.test.ts

@@ -15,7 +15,9 @@ test('app lifecycle runtime runner main deps builder maps lifecycle callbacks',
     onReady: async () => {
       calls.push('ready');
     },
-    onWillQuitCleanup: () => calls.push('cleanup'),
+    onWillQuitCleanup: () => {
+      calls.push('cleanup');
+    },
     shouldRestoreWindowsOnActivate: () => true,
     restoreWindowsOnActivate: () => calls.push('restore'),
     shouldQuitOnWindowAllClosed: () => false,