Root cause: librlottie RleTaskScheduler creates 32 worker threads on first
lottie_animation_from_data call. These pthreads wait in WaitForMultipleObjects(INFINITE)
and never exit. On MinGW, exit()/pthread_join blocks forever.
Changes:
- messagelist: s_icons moved to file-static; cleanupAnimations() clears them,
calling lottie_animation_destroy BEFORE static destruction
- mainwindow: ~MainWindow calls MessageList::cleanupAnimations() after node stop
- main: ShutdownSentinel counts threads at exit; if >4 remaining, calls
ExitProcess(0) to bypass CRT pthread_join hang
- main: if rlottie properly shuts down (<=4 threads), normal return (no ExitProcess)
Evgeny
73be79d204