Function createWebTorrentBackend

createWebTorrentBackend(options: WebTorrentBackendOptions): WebTorrentBackend
Creates a torrent backend that downloads inside the page through a WebTorrent client, which reaches peers over WebRTC only. It announces to the link's wss:// trackers plus the defaults and drops the rest, since a page cannot open the sockets they need (D-017). The backend carries no handoff trait, so describeBridge reports the transfer as kernl's own; peers still see the user's address and what they fetch.
Parameters
- options: WebTorrentBackendOptions
  The client or its loader, trackers, and progress throttling.
Returns WebTorrentBackend
A backend with the job list and controls the Downloads panel uses.
Throws
From add: invalid:info-hash for a hash that is not 40 hex characters, unavailable:<why> when the client cannot load or add.
Example
```
const downloads = createWebTorrentBackend({ client: async () => new (await import('webtorrent')).default() });
const bridge = createTorrentBridge(downloads);
await bridge.resolve(parseLocator(magnetLink), { requester: 'shell' });
downloads.subscribe((jobs) => render(jobs));
```