Add reputation leaderboard cohort privacy guard

[keon0711]

/claim #15

Summary

• Adds a focused reputation leaderboard cohort privacy guard for the Community & User Reputation System.
• Validates whether domain, region, and institution leaderboard cohorts are safe to publish without exposing small-group identity signals.
• Blocks or redacts unsafe cohorts for minimum cohort size, institution diversity, institution dominance, sparse badge combinations, anonymous review credit leakage, contributor opt-out, and volatile score changes.
• Emits deterministic publish/redact/hold decisions plus JSON, Markdown, SVG, and MP4 review artifacts from synthetic data only.

Scope isolation

• This is not another reputation ledger, badge renewal gate, leaderboard eligibility check, endorsement-ring auditor, reputation abuse guard, credit attestation ledger, reviewer workload guard, or transparency receipt module.
• It focuses specifically on privacy-safe publication of reputation leaderboards by domain, region, and institution.

Validation

• node reputation-leaderboard-cohort-privacy-guard/test.js
• node reputation-leaderboard-cohort-privacy-guard/demo.js
• node reputation-leaderboard-cohort-privacy-guard/render-video.js
• node --check reputation-leaderboard-cohort-privacy-guard/index.js
• node --check reputation-leaderboard-cohort-privacy-guard/sample-data.js
• node --check reputation-leaderboard-cohort-privacy-guard/test.js
• node --check reputation-leaderboard-cohort-privacy-guard/demo.js
• node --check reputation-leaderboard-cohort-privacy-guard/render-video.js
• ffprobe -v error -select_streams v:0 -show_entries stream=codec_name,width,height,pix_fmt,duration -of default=nw=1 reputation-leaderboard-cohort-privacy-guard/reports/demo.mp4
• git diff --cached --check

The generated MP4 is H.264, 1280x720, yuv420p, duration 4.000000 seconds.

[keon0711]

@algora-pbc /claim #15

[keon0711]

/claim #15