Interface AssemblyAIRealtimeSocket

The minimal outbound surface of the agent websocket the session depends on. Declaring the seam as an interface lets unit tests inject a fully in-memory fake that captures outbound frames and drives AssemblyAIRealtimeSession.HandleServerEvent with provider-shaped events — no websocket, no network.

interface AssemblyAIRealtimeSocket {
close(): void;
send(data: string): void;
}