The window can't be dragged if a ContentDialog is opened

[MGGSK]

Which version of the app?

WinUI 3 Gallery

Description

Steps to reproduce the bug:

1. Open the ContentDialog sample.
2. Click the "Show dialog" button
3. Try to drag the window

Screenshots

Windows version

Windows 11 24H2 (26052)

Additional context

This issue is probably caused by the content dialog background blocking the title bar.

[karkarl]

I wonder if this this can be repro'd with System TitleBar, since WinUI Gallery currently uses a fully custom "user control" titlebar. Hopefully this will resolve once we switch to the new TitleBar control.