Download Run

Create a temporary download URL for a complete workflow run export. Returns a pre-signed URL pointing to a ZIP archive containing all audio output files produced by the run. The URL is valid for 15 minutes (`expires_at`). The archive is generated on first request and cached for subsequent calls; re-calling this endpoint before expiry returns a new URL for the same cached archive. Only available for runs in `completed` status — returns 409 for runs that are still active or ended in `failed`/`cancelled`. Returns 404 if the run produced no audio files. To download output from a single output node rather than the whole run, use `GET /runs/{run_id}/nodes/{node_id}/download`.