Refine styling of merge conflicts (#31012)

- Improved colors
- Blank out diff hunk gutter highlights in conflict regions
- Paint conflict marker highlights all the way to the gutter

Release Notes:

- Improved the highlighting of merge conflict markers in editors.

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Co-authored-by: Marshall Bowers <git@maxdeviant.com>
Co-authored-by: Cole Miller <cole@zed.dev>
0b7583bae5Nate Butler committed on 6/9/2025, 7:03:19 PM· committed by GitHubparente4bd115
8 files changedLine totals unavailable