Gets the token that cancels the decode: a filter that runs long (an image codec, an inflater) checks it between units of work (a row of blocks, a code-block, a chunk of output) and throws , returning what it rented.
public CancellationToken CancellationToken { get; init; }
Viewer capability 2 (issue #97): building a display list hands its CancellationToken to the decodes of the page's content and images, so a long decode stops when the build is cancelled. The pipeline never turns the exception into a diagnostic. by default and for DecodeStream(CosStream).