Brain API HTTP 502: {
  "ok": false,
  "error": "Academy structured output invalid after round-specific canonicalisation: Academy structured output invalid: unexpected fields: acceptance_criteria",
  "retryable": true,
  "infrastructure_failure": true,
  "output_contract": "academy_round_json_v6",
  "exam_round": 3,
  "raw_answer": "{\n  \"round\": 3,\n  \"transfer_project\": {\n    \"title\": \"Household Corner Fillet Transfer\",\n    \"goal\": \"Apply filleting logic to a non-manifold household object model for s