Fix adding breakpoint/bookmark via gutter context menu using the wrong row (#59269)

# Objective

Fixes #59265

## Solution

Use `display_point_to_anchor` to properly convert `DisplayRow` to
`Anchor`, instead of manually constructing `Point` directly as done
currently.

## Testing

- Tested manually, see video in issue
- Tested on windows

## 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)
- [ ] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

## Showcase


<details>
  <summary>Click to view showcase</summary>

My super cool demos here

</details>

---

Release Notes:

- Fixed the gutter context menu adding breakpoints/bookmarks to the
wrong row in multibuffers.

---------

Co-authored-by: dino <dinojoaocosta@gmail.com>
e9c484165dguopenghui committed on 7/24/2026, 12:20:06 PM· committed by GitHubparent984e3bd
2 files changedLine totals unavailable