Render changed files as expandable tree with aggregated diff stats

- Replace flat changed-files chips in ChatView with a nested, expandable tree
- Extract diff tree/stat logic into turnDiffTree utilities
- Add unit tests for stat aggregation, nesting, and Windows path normalization
d6ed393255Julius Marminge committed on 3/5/2026, 11:56:40 PM· committed by Julius Marmingeparent2d91397
3 files changedLine totals unavailable