Bug: DispatcherQueueSynchronizationContext changes break UnhandledException event in winui apps

[lhak]

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Description

The UnhandledException event handler broken since appsdk 1.7 was released (see https://github.com/microsoft/microsoft-ui-xaml/issues/10447#issuecomment-2800107924) and the issue is caused by a change in the DispatcherQueueSynchronizationContext class. I see that this file also exists in this repo (see here) and has the same bug.

Steps To Reproduce

1. Register for UnhandledException handler in a winui app
2. Throw an exception in the application
3. App crashes without the event being invoked

Expected Behavior

UnhandledException handler should be invoked

Version Info

cswinrt 2.2 appsdk 1.7

Additional Context

No response