file_finder: Debounce file finder refreshes on worktree updates (#60451)

# Objective

Delay picker refreshes for entry updates so bursty filesystem events
trigger only one search refresh, while still refreshing immediately when
worktrees are added or removed.

Update tests to advance both the watch latency and refresh debounce, and
add coverage for coalesced worktree updates.



## 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 adheres to Zed's UI standards
([UX/UI](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
and
[icon](https://github.com/zed-industries/zed/blob/main/crates/icons/README.md)
guidelines)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable



Release Notes:

- N/A

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Co-authored-by: Kirill Bulatov <mail4score@gmail.com>
2fd6e23778Bing Wang committed on 7/21/2026, 11:59:11 AM· committed by GitHubparent869d357
2 files changedLine totals unavailable