App.UnhandledException is bypassed for uncaught desktop window events

App.UnhandledException is intended to be the last-chance handler for uncaught runtime exceptions, but uncaught exceptions raised from desktop window/control events can currently terminate the app without giving App.UnhandledException a chance to suppress them.

For example, a divide-by-zero in Window1.Opened ends the whole app with a runtime error instead of flowing to the application-level handler. This makes App.UnhandledException unreliable as a catch-all safety net for desktop apps.