Brain API HTTP 502: {
  "ok": false,
  "error": "Academy structured output invalid after round-specific canonicalisation",
  "retryable": true,
  "infrastructure_failure": true,
  "output_contract": "academy_round_json_v4",
  "exam_round": 2,
  "raw_answer": "{\"skill_id\":\"parametric_cad.parameter-architecture\",\"name\":\"Parameter architecture\",\"domain\":\"parametric_cad\",\"risk\":\"low\",\"lane\":\"tool_evidence\",\"professional_review\":false,\"round\":2,\"focus\":\"failure diagnosis, provenance and safety