Behaviour for wire-level WhatsApp protocol transports.
A protocol transport owns socket lifecycle and raw node/frame exchange below
the session engine. It must not build high-level message types or bypass
Signal/fanout. ExWapp.Conn is the production implementation.
Do not confuse this layer with ExWapp.Client.Transport, whose historical
name describes a high-level client runtime adapter.
Summary
Types
@type wa_node() :: term()