Possible bug - .NET 10 iOS hangs on line in MAUI code

Not sure how to continue from my current issue or how to diagnose this further. With .NET 10 under iOS my app hangs endless at this line in the MAUI code: https://github.com/dotnet/maui/blob/e7f8f08358ea926d878eaa01b9afbe390fcbe89f/src/Core/src/Handlers/Window/WindowHandler.iOS.cs#L65

I have a LoadingPage, this works so far. After all data is loaded and ready the app creates the AppShell and inserts it via `currentApp.Windows[0].Page = appShell;` with .NET 9 it worked fine this way. Also with .NET 10 on Android. However with .NET 10 on iOS this results in a endless hang at the linked line. No exception, nothing.

I tried to make a minimal repo for it but strangely it worked there.

This was the, very badly translated, result from Copilot for this (not sure if it helps):

```
Das Problem scheint mit der neuen effectiveGeometry-Beobachtung in .NET 10 iOS zusammenzuhängen. Die App hängt sich bei Zeile 65 auf, wenn MapContent aufgerufen wird.
Mögliche Ursache:
Die neue Geometrie-Beobachtung für Mac Catalyst 16+ (Zeilen 147-158) könnte zu einem Deadlock führen, wenn die Seite gesetzt wird, bevor die Fenstergeometrie vollständig initialisiert ist.
```

Start with src/Core/src/Handlers/Window/WindowHandler.iOS.cs at line 65 and reproduce the reported transition from LoadingPage to AppShell via currentApp.Windows[0].Page = appShell on .NET 10 iOS. Compare the behavior with .NET 9 and Android, then reduce the application to a minimal reproduction; done means the hang is reproduced and its cause or a verified fix is established.

Written by the indexing model from the issue text.