InteractiveCodeEstimated ~25 mins
1.3 Offline-Resilient IndexedDB Answer Buffering
### Hands-on Lab: Client Answer Buffer Invariant
Build an offline answer persistence wrapper using browser IndexedDB. When network status is offline, candidate keystrokes are written immediately to IndexedDB and flushed to `/api/v1/exams/attempts/{id}/answers` the moment connection restores.