enterprise: add Phase 5 observability and enterprise features
Observability:
- HTTP health endpoints (/health, /ready, /health/deep)
- Prometheus metrics endpoint (/metrics) with prom-client
- W3C traceparent request tracing with AsyncLocalStorage
- Trace ID propagation to logs and diagnostic events
Enterprise:
- JSONL audit logging with daily rotation and 7-day retention
- RBAC permission engine with flat roles (admin, operator, user, viewer)
- Tool and agent access restrictions per role
- Audit integration with pairing, auth, and exec approval flows
Documentation:
- Enterprise deployment guide (single/multi-tenant, K8s, Docker)
- Security hardening guide (TLS, RBAC, rate limiting)
- Observability guide (Prometheus, Grafana, alerting)
- Self-healing behaviors documentation
Load Testing:
- Connection stress test (WebSocket saturation)
- Chat throughput test (sustained message load)
- Auth stress test (rate limit verification)
- Configurable scenarios with p50/p95/p99 latency metrics
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>