- Refactor TaskChangesTab to use merge commit diff for done/archived tasks instead of branch diff
- Add CommitDiffTab component integration for displaying merge commit changes
- Remove legacy API endpoints and tests for branch-based diff on completed tasks
- Add comprehensive test suite for TaskChangesTab covering all task lifecycle states
- Document merge commit diff behavior in dashboard README
- Create CommitDiffTab component with commit list and inline diff display
- Integrate Commits tab into TaskDetailModal with conditional visibility
- Add comprehensive tests for CommitDiffTab rendering, selection, and diff display
- Add TaskDetailModal tests for tab visibility based on task PR info
- Remove stale changeset and unused store test code