Copilot window can become stuck always on top until app restart

### Description

The GitHub Copilot App somehow entered a persistent topmost window state on Windows. After that happened, the main Copilot window remained in front of every other application when I switched focus, covering those apps.

There was no visible always-on-top or pin control in the title bar or app UI, and I do not have PowerToys installed, so this was not caused by PowerToys' Always On Top feature.

### Reproduction

I do not yet know what action triggered the state. The app had been used normally across multiple sessions and eventually began behaving as an always-on-top window.

### Actual behavior

The Copilot window stayed above all other application windows even after another app received focus.

### Expected behavior

Unless explicitly requested by the user, the Copilot window should follow normal Windows z-order and move behind the active application.

### Workaround

Fully restarting the GitHub Copilot App cleared the topmost state and restored normal window behavior.

### Environment

- GitHub Copilot App: 1.1.10
- Windows: 10.0.26200.0
- PowerToys: not installed

Beginnen Sie damit, das gemeldete persistente Always-on-top-Verhalten unter Windows mit den angegebenen App- und OS-Versionen zu reproduzieren, und untersuchen Sie anschließend die Behandlung des Fensterstatus auf dem Desktop. Stellen Sie fest, welche Aktion oder welcher Lebenszyklus das Fenster topmost belässt, und überprüfen Sie, dass normale Fokusänderungen die standardmäßige z-order wiederherstellen, ohne dass die App neu gestartet werden muss.

Vom Indexierungsmodell aus dem Issue-Text verfasst.