Use QueryClient to execute checkpoint diff query in test

- run `checkpointDiffQueryOptions` through `QueryClient.fetchQuery`
- validate `getCheckpointDiff` call via React Query execution path
200e43e44cJulius Marminge committed on 2/19/2026, 5:59:17 AM· committed by Julius Marmingeparent6aea858
1 file changedLine totals unavailable