Fix bdecode busy-loop on truncated torrent payloads.

Malformed bencode could set pos.i to NaN and hang Jest forever;
guard the decoder and align the no-url-list fixture with current qbt behavior.

__tests__/torrent.test.js

@@ -34,6 +34,17 @@ describe('extractWebseed', () => {
     expect(extractWebseed(Buffer.from('not a torrent'))).toBeNull();
   });
 
+  it('returns null for truncated dict (no busy-loop)', () => {
+    // Previously: dict key "pieces" without value → bdecode infinite loop
+    const truncated = Buffer.from(
+      'd4:infod6:lengthi0e4:name4:teste12:piece lengthi524288e6:piecese',
+      'utf8',
+    );
+    const t0 = Date.now();
+    expect(extractWebseed(truncated)).toBeNull();
+    expect(Date.now() - t0).toBeLessThan(100);
+  });
+
   it('returns null when url-list is missing', () => {
     // Bencode a dict without url-list
     const buf = makeTorrent({ name: 'f.mkv', size: 0, webseedUrl: 'http://x.com/s/a' });