I/O-free core model of the weida messaging framework.
This crate contains no networking, no tokio and no serialization: only the
vocabulary types (endpoint addresses, limits, trace context, errors) that
the wire codec and the transport share. Everything here is unit-testable
without a socket.
The correlation and acknowledgement state machines that used to live here
are gone: Req/Rep rides one bidirectional QUIC stream, so the stream is
the correlation, and delivery is QUIC's own transport receipt rather than an
application-level ACK (docs/ARCHITECTURE.md, layer model).