Brain API HTTP 422: {
  "ok": false,
  "error": "Academy structured output invalid after round-specific canonicalisation: Academy structured output invalid: every Round 3 boundary case must be a meaningful plain-language string",
  "retryable": false,
  "infrastructure_failure": false,
  "content_format_failure": true,
  "failure_class": "academy_output_contract_failure",
  "output_contract": "academy_round_json_v6",
  "exam_round": 3,
  "raw_answer": "{\n  \"round\": 3,\n  \"transfer_project\": {\n    \"title\": \