Virtualize DiffPanel rendering with @pierre/diffs beta

- upgrade `@pierre/diffs` to `^1.1.0-beta.16`
- switch file diff list to `Virtualizer` for smoother large patch rendering
- adjust diff panel container/layout handling and theme typing
4c98219c43Julius Marminge committed on 2/19/2026, 1:56:30 AMparentf748aa8
4 files changedLine totals unavailable