New Node.knockout_shape (transparency.set / object.setProps knockoutShape,
reported by transparency.info). In a knockout group such an object knocks
out only as much as its opacity and mask let through (a 50% object knocks
out 50%); otherwise its full coverage knocks out. The renderer, PDF and
SVG masks honour it, and the panel's checkbox is now live.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>