Extreme year (hot, cold, heatwave, moisture, P90 solar, ...)

Extreme year picked from a range of actual years by the chosen criterion. 1 credit.

Starts a background job and returns {"job_id": ...} immediately. Credits are charged on submission and refunded if the job fails; the balance after the call is in the X-Credits-Remaining response header. Then poll GET /api/jobs/{job_id}, stream /api/jobs/{job_id}/stream, or register a webhook.