## Context

This PR refines the design for all of these Git pickers but making them
look more consistent and polished (using same fonts, dividers, and
alignment). It also adds a delete button to all items in each picker so
you can more intuitively delete each item if you're on a mouse-based
flow.

| Worktrees | Stashes | Branches |
|--------|--------|--------|
| <img width="1490" height="1178" alt="Screenshot 2026-03-23 at 9  15
2@2x"
src="https://github.com/user-attachments/assets/3143a626-1b97-43b5-b769-d6cab2c5df7c"
/> | <img width="1490" height="1178" alt="Screenshot 2026-03-23 at 9  15
3@2x"
src="https://github.com/user-attachments/assets/80cbd5ee-394d-42b7-84f8-2d9950d9889e"
/> | <img width="1490" height="1178" alt="Screenshot 2026-03-23 at 9 
15@2x"
src="https://github.com/user-attachments/assets/408fd12e-fb18-4233-a4bf-5fad53aa307f"
/> |

--- 

- [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

Release Notes:

- N/A