Add viz.html as the main entry point that loads Three.js from CDN and
orchestrates all visualization components (scene, body model, signal
viz, environment, HUD). Add data-processor.js that transforms API
WebSocket messages into geometry updates and provides demo mode with
pre-recorded pose cycling when the server is unavailable.
https://claude.ai/code/session_01Ki7pvEZtJDvqJkmyn6B714
