relay: ensure onclose callback is triggered

[CodyTseng]

1. When ws.onerror or ws.onclose events are triggered before a successful connection (while this._connected is still false), the this.onclose?.() callback was not being called. This prevented the relay from being removed from the pool, making it impossible to reconnect via ensureRelay.

2. Potential error in close sequence: The this.onclose?.() callback was called after this.ws?.close(), which could potentially throw an error and prevent the this.onclose?.() callback from executing.