v2.2.4

Dependency advisories patched (hono → 4.12.27, undici override → 7.28.0, pydantic-settings → 2.14.2; pnpm audit --prod 5 high → 1 high) and a full production-readiness audit with measured load numbers — sustained ~20,000 events/s at p95 81 ms (4× the ≥5k target). See docs/production-readiness/v2.2.3.md.