Windows: every start ended itself after 3 s (1.3.0, 1.3.1)

Win32Window::Create calls Destroy() before it makes the window, which
ran FlutterWindow::OnDestroy and armed the 3 s exit timer at launch: the
window showed, then the process ended with code 0, no crash, no close
lines. The timer is only armed with an engine to tear down. Found and
fixed by Fun Maker's agent on Windows (a debugger caught the exit on the
timer's thread).

The smoke runs missed it (they closed at ~4 s anyway): the app now stays
up 10 s, and the scripts require 'closing' and 'quitting' from its own
close.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/desktop/lib/src/platform/smoke.dart

@@ -12,9 +12,14 @@ import 'ports/player_host.dart';
 // in a session player with a video output through the media pipeline,
 // play a second and close the normal way ([shutDownApp]). Progress goes to
 // `STARSYNC_SMOKE_OUT` (one line per step: `start`, `opened <ms> render=<mode>`,
-// `closing`, or `skip <why>` / `fail <why>`), so the script can tell a
-// runner that cannot show a window (skip) from a close that hangs or
-// leaves a process behind (fail).
+// `closing`, `quitting`, or `skip <why>` / `fail <why>`), so the script can
+// tell a runner that cannot show a window (skip) from a close that hangs or
+// leaves a process behind, or a process that ends on its own (fail). It
+// stays up [smokeUptime] first: a start that dies by itself (the 1.3.0
+// Windows exit timer) ends before `closing`.
+
+/// How long the smoke run keeps the app up before closing it.
+const smokeUptime = Duration(seconds: 10);
 
 /// The smoke run's media, or null for a normal start.
 String? get smokeMedia {
@@ -65,6 +70,9 @@ Future<void> runSmoke(AppGraph graph, String media) async {
   } catch (e) {
     step('fail $e');
   }
+  final wait = smokeUptime - sw.elapsed;
+  if (wait > Duration.zero) await Future.delayed(wait);
   step('closing');
-  await shutDownApp();
+  // Reached only through the app's own close (not a kill on the way).
+  await shutDownApp(beforeQuit: () async => step('quitting'));
 }