Handle changing root paths without splitting in the sidebar (#53566)

Self-Review Checklist:

- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

Closes #ISSUE

Release Notes:

- N/A

---------

Co-authored-by: Eric Holk <eric@zed.dev>
4a1fb25f67Mikayla Maki committed on 4/10/2026, 1:21:19 AM· committed by GitHubparent3436e51
6 files changedLine totals unavailable