continuation-token-pagination-contract

Model an endpoint that returns a page plus a next-token as Flow<Resource<Pair<items, token?>>> — a null token means the end, the caller stores only the token, and a bounded prefetch primes the first pages before anything is shown. Use when wiring an opaque-cursor API into a repository, or when a list stops loading after one failed request and never recovers, or when paging fires twice for one trigger.