WinAppSdk 1.6 Multi monitor Incoming Toast notification

### Describe the bug

With 2 monitors attached in “duplicated display” mode, any Toast notification goes to notification center rather than appearing directly on screen
The expectation is that it should show up on the main screen

### Steps to reproduce the bug

1. Attach 2 monitors to the same computer in "duplicate display" mode
2. Send a Toast in any WinAppSdk 1.6 (WinUI3) app

### Expected behavior

The expectation is that it should show up on the main screen

### Screenshots

_No response_

### NuGet package version

None

### Packaging type

_No response_

### Windows version

_No response_

### IDE

_No response_

### Additional context

_No response_

No source file or test is named in the issue. Start by reproducing a WinAppSdk 1.6 WinUI3 toast with two monitors in duplicated-display mode, then trace the toast notification handling; done means the toast appears directly on the main screen instead of only in Notification Center.

Written by the indexing model from the issue text.