Bug Description

WebSocketStream can throw TypeError [ERR_INVALID_STATE]: Invalid state: Controller is already closed when the readable side is canceled and the connection later completes a clean close handshake.

The failure happens because readable.cancel() closes the internal ReadableStreamDefaultController, and the clean socket close path later calls close() on the same controller again.

Reproducible By

1. Start a WebSocket server.
2. Connect with new WebSocketStream(url).
3. Wait for wss.opened and get readable.
4. Call await readable.cancel(new Error('client cancel')).
5. Trigger a clean close, for example with wss.close() on the client and ws.close(1000, 'bye') on the server.
6. Wait for the socket to close.

Minimal reproduction:

const { WebSocketServer } = require('ws')
const { WebSocketStream } = require('undici')

const server = new WebSocketServer({ port: 3000 })
server.on('connection', (ws) => {
  setTimeout(() => {
    ws.send('hello')
    setTimeout(() => ws.close(1000, 'bye'), 20)
  }, 200)
})

;(async () => {
  const wss = new WebSocketStream('ws://127.0.0.1:3000')
  const { readable } = await wss.opened

  await readable.cancel(new Error('client cancel')).catch(() => {})
  wss.close()
  await wss.closed.catch(() => {})
})()

Expected Behavior

Canceling the readable side before a later clean close should not throw or surface an uncaught exception. The connection should close normally and settle closed without crashing the process.

Logs & Screenshots

TypeError [ERR_INVALID_STATE]: Invalid state: Controller is already closed
    at ReadableStreamDefaultController.close (node:internal/webstreams/readablestream:1068:13)
    at #onSocketClose (.../lib/web/websocket/stream/websocketstream.js:389:38)

Environment

Linux
Node.js v22.x
undici main branch

Additional context

The clean close path in lib/web/websocket/stream/websocketstream.js currently calls this.#readableStreamController.close() directly. That is not safe after ReadableStream.cancel() because the controller is already closed at that point.