README: cut the demo GIF placeholder

The GIF was dropped, so the TODO comment was pointing at work that
isn't happening. Comments are visible to anyone reading the raw file,
and the repo is now linked from a live forum thread.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PZnUXRsLLnt2A7pR3X4Luj