Unify compact subheaders and diff file navigation

- Add shared compact subheader styling for preview, file, and diff panels
- Open diff files in the thread file viewer when available
- Fix macOS cursor auto-hide and Option-modified shortcut matching
c2d44a312cJulius Marminge committed on 6/15/2026, 10:58:03 PMparentde8bdc1
17 files changedLine totals unavailable