Report stale corpus labels

[heznpc]

Summary

• report stale corpus labels when manifest fingerprints no longer match current findings
• expose stale label counts and fingerprint IDs in validation JSON and Markdown
• make strict validation fail on stale labels so private release evidence cannot silently rely on old reviews

Real corpus check

• corpus: 64 real instruction documents, 51 roots, 13 holdout documents, 3,359 lines
• current private manifest: 29 report findings, 0 reviewed, 29 unreviewed, 0 stale labels
• review item load remains 8.6 per 1,000 lines and risk finding load remains 19.4 per 1,000 lines
• strict mode exits 1 as expected because usefulness remains unlabeled/unmeasured

Verification

• npm test
• npm run validate:corpus
• node scripts/validate-corpus.mjs --manifest /tmp/rulemeter-real-corpus/manifest.json --format json --out /tmp/rulemeter-real-corpus/result.stale-label-detection.no-text.json
• node scripts/validate-corpus.mjs --manifest /tmp/rulemeter-real-corpus/manifest.json --format json --strict --out /tmp/rulemeter-real-corpus/result.stale-label-detection.strict.json exits 1 as expected
• npm run dogfood
• npm run pack:check
• npm run smoke:install
• npm audit --audit-level=high