Add endorsement ring guard

[swhan0329]

/claim #15

Summary

• Adds a self-contained endorsement ring guard for SCIBASE issue Community & User Reputation System #15.
• Validates endorsement events before they update public reputation scores, badges, or leaderboards.
• Holds reciprocal endorsement pairs, self-endorsements, same-institution concentration, missing-evidence endorsements, and invalid weights for reviewer action.
• Emits reputation deltas only for accepted endorsements backed by typed evidence records.
• Includes runnable tests, a demo script, requirements mapping, acceptance notes, SVG preview, and an H.264 demo video.

Scope notes

• This is intentionally scoped to pre-score endorsement integrity and ring detection.
• It avoids broad community reputation ledgers, peer-review assignment governance, review calibration, credit attestation, reputation transparency receipts, correction impact ledgers, abuse appeals, and mentorship ladders already represented by other submissions.

Validation

• node endorsement-ring-guard/test.js
• node endorsement-ring-guard/demo.js
• node --check endorsement-ring-guard/index.js
• node --check endorsement-ring-guard/test.js
• node --check endorsement-ring-guard/demo.js
• ffprobe -v error -show_entries format=duration,size -show_entries stream=codec_name,width,height -of default=noprint_wrappers=1 endorsement-ring-guard/demo.mp4
• git diff --check
• git diff --cached --check

Demo video: H.264, 1280x720, 5 seconds.

AI-assisted with Codex, reviewed and locally verified before submission.

[swhan0329]

@algora-pbc /claim #15

[swhan0329]

/claim #15