Discards the call's queued outbound audio (sends Vonage's {"action":"clear"} text command).
Registers the inbound PCM16 audio handler for the call's binary media frames.
Registers the inbound control-event handler for the call's JSON text frames (DTMF / connected / close).
Ensures a channel exists for a call (called when a bridge session for the call starts).
Sends one outbound PCM16 audio frame as a BINARY websocket message (raw L16 PCM, no envelope).
Coordinates Vonage media websockets with the bridge bindings, keyed by call UUID.