teeny-request throws when response handler destroys the request stream

### Library Name

`teeny-request` 10.1.3

### Try this API

Not applicable. This is a local Node.js stream lifecycle failure in `teeny-request`; the remote HTTP response succeeds.

### Minimal reproduction

https://gist.github.com/rockwotj/a629eea7b9ccbd7e354659b9f09fead3

Run:

```sh
npm install teeny-request@10.1.3 nock
node repro.js
```

On Node.js 24.16.0 this reports an unhandled rejection:

```text
Error [ERR_STREAM_UNABLE_TO_PIPE]: Cannot pipe to a closed or destroyed stream
```

### Steps and root cause

1. Start consuming the stream returned by `teenyRequest()`.
2. Destroy that stream from its `response` event handler. Retry wrappers do this when discarding a response before another attempt.
3. `teeny-request` then runs its later `response` listener and calls `pipeline(responseStream, requestStream)` with the destroyed destination.
4. Node rejects the pipeline setup with `ERR_STREAM_UNABLE_TO_PIPE`; the rejection is not handled, and the response body is not disposed.

The stream-mode implementation defers piping until both reading has begun and the fetch response exists, but it does not recheck whether the returned request stream was destroyed by an earlier `response` listener.

### Expected behavior

If the consumer destroys the returned stream before piping starts, `teeny-request` should skip pipeline construction and destroy the unused response body. No unhandled rejection should escape.

This is the same production stack previously reported in googleapis/teeny-request#351 and googleapis/teeny-request#352. Those reports were automatically closed for lacking a runnable reproduction.