Function stream_event 

pub fn stream_event(
    pair: TransformPair,
    ctx: &TransformContext,
    data: &str,
) -> Result<Vec<StreamEventOut>, TransformError>

Convert one decoded stream event (upstream wire JSON text → inbound event). Same reverse-pair convention as response_bytes. Only content-generation pairs stream; the other groups are buffered. This convenience call retains no cross-frame state; use StreamConverter for an actual response stream.