extensions_ui: Prevent extension tags from overlapping actions (#63153)

# Objective

Prevent extension feature tags from overlapping card actions when
horizontal space is constrained.

## Solution

Let the metadata row shrink and clip while reserving space and a gap for
the action buttons.

## Testing

- `cargo fmt --check`
- `cargo test -p extensions_ui`
- `./script/clippy -p extensions_ui`
- `git diff --check`

## 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
- [ ] Tests cover the new/changed behavior (layout-only change;
before/after videos to follow)
- [x] Performance impact has been considered and is acceptable

## Showcase

Before


https://github.com/user-attachments/assets/4268ff59-d1ec-4081-b977-c748e2dd8351

After


https://github.com/user-attachments/assets/d8617b90-45e2-41b4-9504-7eb8a808e5e2

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Release Notes:

- Fixed extension tags obscuring action buttons on extension cards.
1747596aa0Josh Kent committed on 8/24/2026, 8:20:04 PM· committed by GitHubparentff7b061
1 file changedLine totals unavailable