Getting ExtendsContentIntoTitleBar value will cause unicolor title bar since WASDK 1.6

[whiskhub]

Describe the bug

Since Windows App SDK 1.6, the title bar of a window will turn completely unicolor, if AppWindow.ExtendsContentIntoTitleBar is read (yes, just getting the value, not even setting it).

If the Windows color mode is set to dark, the title bar will be completely black; for light mode completely white. There will be NO Mica effect on the title bar.

This is a regression - in Windows App SDK 1.5 this is not reproducible.

Steps to reproduce the bug

1. Create blank WinUI 3 app with Windows App SDK 1.6 (with the necessary WindowsSdkPackageVersion stuff...)
2. Add the following line in the MainWindow constructor:
   var unusedVariable = AppWindow.TitleBar.ExtendsContentIntoTitleBar;
3. Optional: Add Mica backdrop to the Window, so the color difference is more easily visible.
4. Start the app without a debugger (to avoid WinUI 3 app started via debugger will always have unicolor (black) title bar #9987)
5. You will see a unicolor (black/white) title bar.

Expected behavior

1. Getting the AppWindow.TitleBar.ExtendsContentIntoTitleBar should not change anything with the title bar (color). Especially the Mica effect shall be retained.
2. Upgrading from WADSK 1.5 to 1.6 shall not cause this breaking change.

Screenshots

Title bar with get AppWindow.TitleBar.ExtendsContentIntoTitleBar:

Titlebar without get AppWindow.TitleBar.ExtendsContentIntoTitleBar:

NuGet package version

WinUI 3 - Windows App SDK 1.6.0: 1.6.240829007

Windows version

Windows 11 (22H2): Build 22621

Additional context

No response