Settings Window Can't close when Copilot auto starts with Xcode

**Describe the bug**

Settings Window of Copilot can't close. If you choose close button on the top-left, it hides but doesn't close. You can find the app icon on the dock. When you click the app icon, the Settings Window shows again.

This issue even exists with two windows, Settings Window and Chat Window. When both of them are opened, closing Settings Window still doesn't close. Further more, you can't open the Settings Window from Chat Window as there has already been one opened.

If you choose quit in Settings Window, the whole copilot app will be closed.

**Versions**
- Copilot for Xcode: 0.43.0
- Xcode: 26.0 beta 7 (17A5305k)
- macOS: 26.0 Beta (25A5351b)

**Steps to reproduce**
1. Quit Copilot, Quit Xcode
2. Open Xcode, and let Copilot auto starts with Xcode.
3. Open Settings Window from Copilot

If you quit Copilot and manually open it. This issue doesn't exist as Chat Window is opened first in this way.

**Screenshots**

**Logs**

**Additional context**