The per-target middleware chain (slots, dispatcher, mutation gate, metadata
merger), body capture, access-log terminal sink, and the proxy wiring that
builds + runs chains for synthesized agent-network services.
* **New Features**
* Access logs now include bytes_upload and bytes_download (API and schemas updated, fields required).
* Certificate issuance duration is now recorded as a metric.
* **Refactor**
* Metrics switched from Prometheus client to OpenTelemetry-backed meters; health endpoint now exposes OpenMetrics via OTLP exporter.
* **Tests**
* Metric tests updated to use OpenTelemetry Prometheus exporter and MeterProvider.
* Fix WebSocket support by implementing Hijacker interface
Add responsewriter.PassthroughWriter to preserve optional HTTP interfaces
(Hijacker, Flusher, Pusher) when wrapping http.ResponseWriter in middleware.
Without this delegation:
- WebSocket connections fail (can't hijack the connection)
- Streaming breaks (can't flush buffers)
- HTTP/2 push doesn't work
* Add HijackTracker to manage hijacked connections during graceful shutdown
* Refactor HijackTracker to use middleware for tracking hijacked connections
* Refactor server handler chain setup for improved readability and maintainability
