Function stashed_answer 

async fn stashed_answer(
    peek_uuid: Uuid,
    upload: StashUpload,
    tail: Vec<(Row, NonZeroI64)>,
) -> PeekResponse

Writes tail, the rows the walk still held when it ended, to upload, finishes it, and builds the response that names the stashed batch.

The tail goes to the stash rather than beside the handle, so that a stashed answer carries no rows inline: the tail can hold up to the batch size, and the controller merges every worker’s inline rows into one response that environmentd holds whole. It rides the flush the upload pays anyway.