Consolidates three separate cron jobs into one efficient skill-health.ts job:

• Only checks originals (non-duplicate skills) - ~47K instead of ~94K
• Checks if skill still exists via HEAD request
• When original is deleted, promotes oldest duplicate to become new original
• Backfills firstCommitAt if missing
• Tracks lastCheckedAt to skip recently-checked skills

• Added to skills table
• Indexed for efficient queries
• Run migration before deploying: database/run-migrations.ts

• Only processes skills not checked in last 24 hours
• Orders by oldest-checked-first
• 500 skills per run

1. Run migration: database/run-migrations.ts
2. Deploy skill-health.ts
3. Set interval (recommended: every 15 minutes)
4. Monitor for 24-48 hours
5. Disable old jobs:
   • cron/refresh-skills.ts
   • cron/deduplicate.ts
   • cron/track-change-history.ts

When an original skill is deleted:

Original (deleted) ──┬── Duplicate A (firstCommit: Jan 5)  ← promoted to original
                     ├── Duplicate B (firstCommit: Jan 8)  ← stays duplicate of A
                     └── Duplicate C (firstCommit: Jan 10) ← stays duplicate of A

The oldest duplicate by firstCommitAt becomes the new original. Other duplicates remain duplicates (now of the promoted skill).

1. Content change detection: Currently we don't detect if skill content changed. Could add If-Modified-Since headers to detect updates.

2. Duplicate chain cleanup: When original is deleted and promoted, the "duplicate of" relationship isn't explicitly stored. All duplicates with same contentHash are treated as peers.

3. Verified skill priority: Could prioritize verified skills when promoting instead of oldest.