Revamp the line patch dialog to improve usability and clarity. Improve accessibility and German/English localization for UI text. Add toolbar, hunk navigation, per-line checkbox selection and footer. Extract merge-in-progress UI into a reusable merge progress notice. - Replace selection UI with checkboxes, range selection, and counts - Add hunk navigation, active-hunk tracking, and scroll synchronization - Extract merge-in-progress UI into a reusable notice component