Fix react-pacer import and initialize diff state in test

- update `useDebouncedValue` import to `@tanstack/react-pacer`
- add missing `diffThreadId`, `diffTurnId`, and `diffFilePath` in thread continuity test state
46e540f52dJulius Marminge committed on 2/18/2026, 9:18:13 AMparent8307207
2 files changedLine totals unavailable