Every turn in the same session as transcript_id, oldest first.

Powers "Open original conversation" in the jobs panel: a job points at a single transcript (one turn), but the user wants to replay the WHOLE conversation that turn belonged to. Turns are grouped by session_id (the SDK session id, stable across multi-turn resume — same grouping key as /api/sessions); a transcript with NULL session_id is its own single-turn thread. RLS-scoped to the caller's tenant + user. Returns the anchor id so the client can scroll the replay to the job's turn.