fix(connect/ws): ensure proxy stream is writable (#2024)

Here the proxy stream is being written, so we need to check if it is
writable ("which means the stream has not been destroyed, errored, or
ended, see
https://nodejs.org/dist/v18.19.0/docs/api/stream.html#writablewritable
).

Fixes #1914

I could reproduce the 'stream.push() after EOF' error in an app, but
unfortunately have no idea how to use it for a reproduction. Hopefully
this patch provides enough inspiration to write a test.

Author: jzaefferer

src/lib/connect/ws.ts

@@ -256,7 +256,7 @@ const browserStreamBuilder: StreamBuilder = (client, opts) => {
 	 * https://developer.mozilla.org/en-US/docs/Web/API/WebSocket/message_event
 	 */
 	async function onMessage(event: MessageEvent) {
-		if (!proxy || proxy.destroyed || !proxy.readable) {
+		if (!proxy || !proxy.readable || !proxy.writable) {
 			return
 		}
 		let { data } = event