Gateway

When a stack declares a gateway.<provider> block, stackied does not spawn a child process. Instead it calls spaceport::build_gateway_router, binds the returned axum::Router to a TCP listener on the allocated port, and owns the serving future for the lifetime of the block.

The GatewayRegistry tracks every live gateway by name, holding both the tokio::task::JoinHandle (so it can be awaited or aborted on shutdown) and a tokio_util::sync::CancellationToken (so graceful shutdown can be signalled through axum’s with_graceful_shutdown future).