Stream the spans of a single trace as CSV or JSONL (sync export)

Cursor-streamed synchronous export of every span belonging to the trace identified by trace_id. trace_id is required — the batch “all traces” export path was removed because it was too expensive to support at hypertable scale. Callers needing trace- level analytics should use GET /v1/traces for paginated listing and call this endpoint per trace.

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, name, type, model, duration_ms, prompt_tokens, completion_tokens, cost_usd, span_output, trace_output, error, created_at. span_output is the span’s own output payload; trace_output is the parent trace’s output payload joined onto every span row so a single download carries both.

JSONL emits one JSON object per line with the same keys.

The Content-Disposition filename is spans-<trace-prefix>-YYYY-MM-DD.{csv,jsonl}.