Function wsMessages

Wrap a WebSocket-like object as an async iterable of message events.

Supports both browser-style WebSocket (addEventListener/removeEventListener) and Node.js EventEmitter-style (on/off).

• Returns cleanly when the socket emits 'close'.
• Throws when the socket emits 'error'. Any messages received before the error are yielded first; the error is thrown when the consumer tries to read the next message. Consumers should wrap the for-await loop in try/catch to distinguish clean close from connection failure (and decide whether to reconnect).