Open diff files in editor from diff header clicks

- Add click handling on diff file headers (`data-title`) to open files via native `openInEditor`
- Resolve file paths against active thread/project cwd before launching editor
- Add header hover affordance and tighten diff panel spacing
9a30a50807Julius Marminge committed on 3/1/2026, 5:23:50 AMparent206eb6a
1 file changedLine totals unavailable