ReceiptFrame
dataclass #
client → hub: ack or nack a notify.
recipient_id names the agent acknowledging delivery — required because a single endpoint may host several registered identities, and the hub must know whose cursor to advance. Mirrors :attr:NotifyFrame.recipient_id. channel_id names the channel the acked envelope belongs to; the hub keeps one cursor per (recipient, channel), so an ack that omits it cannot be attributed and is dropped.
status is "ack" (the agent has processed the envelope; the hub advances that recipient's cursor for the channel so it is not replayed on reconnect) or "nack" (the agent could not process it; the hub leaves the cursor untouched and surfaces a dispatch-failure event to listeners). reason is a free-form diagnostic.