- **project_search: Add failing test for regex searches with
assertions**
- **project_search: Improve handling of regex assertions**

# Objective

Fixes #55995 by removing a faulty optimization path for regex searches.


## Solution

## Testing

We've added 3 extra tests for the changed behavior.

## 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

## Showcase

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Release Notes:

- Improved handling of regexes in project/buffer searches

---------

Co-authored-by: Smit Barmase <heysmitbarmase@gmail.com>