ConstReadonlyGoingAway: 1001RFC 6455 going-away (1001): endpoint is leaving.
ReadonlyNormal: 1000RFC 6455 normal closure (1000): orderly shutdown, e.g. reconnection or room expiry.
ReadonlyPolicyViolation: 1008RFC 6455 policy violation (1008): auth failure, rate/room-full rejection, wrong-node redirect, or kick.
WebSocket close codes the server uses when disconnecting peers.