pub const DONE_SENTINEL: &str = "data: [DONE]\n\n";Expand description
The SSE stream-terminator sentinel.
Must be sent by the caller exactly once, only after the entire event
stream from SseEncoder::encode is truly exhausted — never bundled
into an individual event’s encoding, since LlmStreamEvent::Done is
not guaranteed to be the last event (a trailing
LlmStreamEvent::Usage can legitimately follow it) and nothing may
be sent after [DONE] on the wire.