The health check endpoint listens on a dedicated HTTP server.
By default, it is available at 0.0.0.0:9000/health. This can be configured using the --health-listen-address flag.
The results are cached for 3 seconds to avoid excessive calls.
The health check performs the following:
Checks the number of active listeners.
Validates each listener via WebSocket and QUIC dials, including TLS certificate verification.
