- Add backend API endpoint /api/tasks/:id/diff for file diffs
- Add useChangedFiles hook for fetching and managing diff state
- Create ChangedFilesModal component with file list and diff viewer
- Integrate modal with TaskCard via files changed badge click
- Add CSS styling for changed files layout and diff display
- Add keyboard navigation (Escape to close)
- Include unit tests for ChangedFilesModal component
- Add backend API endpoint to get changed files and diffs for a task worktree
- Add useChangedFiles hook for fetching and managing diff data
- Create ChangedFilesModal component with file list and diff viewer
- Integrate modal into TaskCard with click handler to view changes
- Add frontend API integration and type definitions
- Include unit tests for hook and modal components
- Add changeset for the new feature
- Remove deprecated mission-related test files
