Function render_jsonl 

pub fn render_jsonl<I, W>(events: I, w: &mut W) -> Result<()>
where
    I: IntoIterator<Item = Result<TranscriptEvent>>,
    W: Write,

Streams events as JSON Lines to w, flushing after each event.

The flush is deliberate: a streaming backend can emit a Partial half a second before its Final and a downstream tail -f consumer should see it without waiting for the next event to push it through stdio buffering.