`AppLifecycleListener.onExitRequested` never fires on Windows after `pdfrxFlutterInitialize()`

[Markus43]

Summary

On Windows, once pdfrxFlutterInitialize() has run, closing the window with the title-bar X no
longer triggers AppLifecycleListener.onExitRequested, so apps can't run graceful shutdown. It
happens from init alone, before any PDF is rendered, and reproduces on the latest versions.

Environment

pdfrx 2.4.7, pdfrx_engine 0.4.6, Flutter 3.44.7 (stable), Windows 10.

Repro

1. Windows desktop app that registers:

   AppLifecycleListener(onExitRequested: () async {
     debugPrint('FIRED');
     return AppExitResponse.exit;
   });

2. Close with the X → prints FIRED.
3. Add await pdfrxFlutterInitialize(); in main(), run again, close with the X.

Expected: still prints FIRED. Actual: never prints; the app just exits.

Note

After pdfrxFlutterInitialize(), the process owns an extra hidden top-level window
(GDI+ Hook Window Class); removing the init call removes the window and restores
onExitRequested. This appears to defeat the Windows engine's last-window exit check.