copilot: Un-globalify copilot + handle it more directly with EditPredictionStore (#46618)

- **copilot: Fix double lease panic when signing out**
- **Extract copilot_chat into a separate crate**
- **Do not use re-exports from copilot**
- **Use new SignIn API**
- **Extract copilot_ui out of copilot**

Closes #7501

Release Notes:

- Fixed Copilot providing suggestions from different Zed windows.
- Copilot edit predictions now support jumping to unresolved
diagnostics.
ca23fa7c7cPiotr Osiewicz committed on 1/14/2026, 2:44:13 PM· committed by GitHubparentcd12d45
33 files changedLine totals unavailable