Add challenge closeout retention guard

[Davidrsdiaz]

/claim #18

Summary

• Adds a distinct challenge closeout retention guard for the Scientific Bounty System.
• Validates post-award, cancelled, and no-award closeout records for data-room access revocation, restricted dataset destruction/return/legal-hold evidence, appeal-record retention, settlement-gated IP transfer, private-challenge disclosure redaction, and solver compensation/no-award rationale.
• Emits deterministic JSON, Markdown, SVG, and MP4 reviewer artifacts from synthetic closeout records.

Non-overlap

This is separate from existing broad bounty-system, intake compliance, rubric readiness, scoring/arbitration, appeal, payout eligibility, sponsor reliability, IP-redaction preview, data-room access grant, cancellation/no-award, solver withdrawal, reviewer workload, prequalification, benchmark leakage, and award-transparency submissions. It focuses specifically on the final post-challenge closeout boundary: revocation, destruction/return evidence, retention policy, settlement-gated IP transfer, and public disclosure readiness.

Demo Artifact

• scientific-bounty-system/challenge-closeout-retention-guard/artifacts/demo.mp4
• Reproducible with node scientific-bounty-system/challenge-closeout-retention-guard/make-demo-video.js

Validation

• node scientific-bounty-system/challenge-closeout-retention-guard/test.js
• node scientific-bounty-system/challenge-closeout-retention-guard/demo.js
• node scientific-bounty-system/challenge-closeout-retention-guard/make-demo-video.js
• ffprobe scientific-bounty-system/challenge-closeout-retention-guard/artifacts/demo.mp4 -> H.264, 640x360, 5s, 60 frames
• git diff --check

Synthetic data only. No credentials, private sponsor data, solver IP, protected health information, payment processor calls, external APIs, or network calls are used by the module.