Make `copilot::SignIn` open sign-in modal when needed (#30239)

Also:

* Makes sign out show status notifications and errors.
* Reinstall now prompts for sign-in after start.

Addresses some of #29250, but not all of it.

Release Notes:

- N/A
e9a756b5fcMichael Sloan committed on 5/8/2025, 2:52:07 PM· committed by GitHubparent203cb7a
3 files changedLine totals unavailable