src/preview-demo answers a demo.invalid homeserver from fixtures through a guarded fetch;
own-origin requests pass, every other origin is refused (fetch, WebSocket, XHR, beacon).
Built in only with VITE_PREVIEW_DEMO=1 and switched on by previewDemo in config.json
(scripts/preview-config.js --demo, run by the dev workflow). Login prefills 'demo'.
Pose art: 24 downscaled thumbnails in preview-demo/poses, copied into dist by the workflow.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>