WebSocket hibernation needs acceptWebSocket, not accept, or duration billing keeps running

Calling accept() on a WebSocket inside a Durable Object keeps the object resident for the life of the connection and duration charges accrue the whole time. Calling ctx.acceptWebSocket(server) instead hands the socket to the runtime, which can evict the object while the connection stays open and rebuild it when a message arrives.

With hibernation the handlers move off the socket and onto the class: implement webSocketMessage, webSocketClose and webSocketError as methods rather than adding event listeners. In-memory state does not survive hibernation, so whatever a message handler needs must live in storage or in the per-socket attachment set through the serialize attachment method. ctx.getWebSockets() returns the live sockets after a rebuild, which is how a broadcast finds its audience.