fix: stabilize compound-engineering component counts

[tmchow]

Summary

• remove exact component counts from committed release metadata descriptions so skill and agent additions do not cause routine merge conflicts
• keep release validation count-aware by reporting live filesystem totals during validation
• replace exact README totals with durable thresholds and remove exact per-category agent counts

Testing

• bun run release:validate
• bun test tests/release-metadata.test.ts
• bun test