Starts the agent's session in the room. On ANY failure the lease is released and the agent-session row is closed before the error is rethrown; on success the lease is released when the session ends.
Puts an agent into a room for the handoff engine: an agent taking a conversation over, or the first agent of a web
room. The engine's AgentStarter seam. An agent joining a PHONE call holds its own capacity slot (it is a live model
session); a web room is not a phone call and takes none.
Starts agent sessions in LiveKit rooms. One instance per server.