Scope checkpoint diff cache keys to avoid collisions

- Include `cacheScope` in checkpoint diff query keys
- Pass turn/conversation-specific scopes from `ChatView` and `DiffPanel`
- Add tests for key separation and API argument forwarding
4768668637Julius Marminge committed on 2/18/2026, 9:30:38 AMparent46e540f
4 files changedLine totals unavailable