Node Diagnostics Telemetry

Zero-instrumentation HTTP observability with no APM vendor and no logging code in the handlers at all. Everything is observed from outside through the diagnostics channels Node core already publishes: http.server.request.start and response.finish for inbound requests, undici:request:create for outbound fetch, and net.server.socket for connection counts, with request ids from AsyncLocalStorage so an outbound call correlates to the request that made it. Emits JSON logs, per-route latency histograms, and a Prometheus /metrics endpoint. Documents two real behaviors on current Node: bindStore on http.server.request.start does not propagate for server requests so it uses enterWith in a synchronous subscriber, and response.finish can fire outside the request context so it correlates through a WeakMap keyed by the request object. Zero dependencies.