[codex] Add scientific bounty amendment control

[newmattock]

/claim #18

Summary

• add a self-contained scientific bounty amendment-control module
• detect material sponsor changes after solver work begins, including deadline, rubric, IP policy, prize, and visibility/prequalification changes
• emit severity-ranked findings, solver notification packets, evaluation/reviewer/payout hold decisions, signed audit events, and deterministic evidence digests
• include synthetic challenge data, requirement mapping, SVG/GIF demo artifacts, a short MP4 demo video, CLI demo, and Node tests

Distinctness

This slice focuses on sponsor-side challenge amendments after a bounty is already live and before evaluation or payout readiness proceeds. It avoids duplicating existing challenge intake, scoring, arbitration, appeals, workspace privacy, anti-collusion, escrow settlement, and reproducibility-audit submissions.

Demo

• scientific-bounty-amendment-control/docs/demo.mp4
• scientific-bounty-amendment-control/docs/demo.gif
• scientific-bounty-amendment-control/docs/demo.svg
• cd scientific-bounty-amendment-control && npm run demo

Validation

• npm run check
• npm test
• npm run demo
• npm run demo:gif
• git diff --check
• verified docs/demo.mp4 is ISO Media MP4
• verified docs/demo.gif renders as 960x540 GIF

AI-assisted with OpenAI Codex; I reviewed and locally verified the diff before submitting.