- Replace fixed max-height on modal overlay with calc(100vh - 4rem) to prevent content from overflowing viewport
- Add regression tests for ChangesDiffModal height constraint behavior
- Ensures modals stay within visible area regardless of content size
- Create ChangesDiffModal component with unified/split diff views, syntax highlighting, and file stats
- Add expand button to TaskChangesTab to open changes in full-screen modal
- Add comprehensive CSS styles for diff modal, line numbers, and responsive layout
- Add full test coverage for ChangesDiffModal (rendering, diff modes, navigation, keyboard shortcuts)
- Add expand button tests to TaskChangesTab test suite
