Transport implementation for iostream adapter connections.
Communicates with an external process that owns the underlying I/O (SSH channel, TCP socket, WebSocket, etc.). The adapter process handles framing and delivers complete protocol messages.
Protocol:
- Bridge sends
{:iostream_bridge, bridge_pid}during init. - Adapter sends
{:iostream_data, binary}for incoming data. - Bridge sends
{:iostream_send, iodata}for outgoing data. - Adapter sends
{:iostream_closed, reason}on transport close.