requireDoneSentinel

when true, a stream that closes having emitted at least one AiChunk. Token but never a data: [DONE] line is reported as AiChunk.Failed (reason AiFailure. Network, AiChunk.Failed.detail naming the partial length) instead of success — for a backend whose contract guarantees [DONE] as the terminal event. Defaults to false because [DONE] is otherwise optional in this provider's wire contract (see class doc) — a backend that never sends it and simply closes the connection on a clean finish would otherwise misreport every successful reply as cut off.