Stream dataset items as CSV or JSONL (sync export)

Cursor-streamed synchronous export of items in the named dataset. Rows are written directly to the response body — never buffered — and capped per plan (Starter: 100, Pro/Team/Business: 5000, Enterprise: unlimited). Hitting the cap sets X-TruLayer-Truncated: true; the payload is complete up to that row.

CSV columns (in order): id, trace_id, span_id, label, created_at. A stored label of NULL surfaces as the literal string unlabeled in CSV and as JSON null in JSONL so the column is never blank.

The optional label query parameter filters by review label (pass, fail, unlabeled) — all (the default when omitted) applies no restriction.