Diff checkbox redesign

[Jordonbc]

No description provided.

[github-actions]

No blocking or important issues found.

• diffView.ts’s new segment-based DOM still keeps state.currentDiffHunkNodes, checkbox syncing, and event handlers aligned with the selection logic, so hunk/line toggles should behave as before.
• The refreshed components.css layout and gutters match the new markup but don’t rely on removed selectors, and the header/context rows remain styled via the existing .hline rules.
• The sentry-log downgrade in Backend/Cargo.toml simply keeps the whole Sentry stack on 0.47; the lockfile now only references those versions and won’t pull in multiple sentry-core copies.

opencode session  |  github run

[github-actions]

No blocking or important issues were identified in this pull request; the new diff markup and styles appear consistent with the selection logic and no API/behavior regressions stood out during the review.

opencode session  |  github run