Docs: sync the embedded app code for the fullscreen fix

[SandObserver]

Summary

• Refresh the embedded app code from SandObserver/Stackyard main via npm run sync-widgets.
• public/js/utils.js: the Allow Fullscreen switch now strips fullscreen from the frame's allow list, and allow is omitted when nothing is left.
• The other public/js/ files change only in cache-busting stamps.

Testing
npm run build and npm run check pass. No visual change.

Checklist

• npm run build and npm run check both pass.
• Product UI is shown by running or capturing it, never recreated in CSS.
• Any new preview or screenshot carries no private hostnames or real data.
• Visual changes verified in both colour schemes and both docs themes.
• Links to the app repo still resolve.

[cloudflare-workers-and-pages]

Deploying stackyard-docs with    Cloudflare Pages

Latest commit:	326bf60
Status:	✅  Deploy successful!
Preview URL:	https://1a56bf61.stackyard-docs.pages.dev
Branch Preview URL:	https://docs-sync-fullscreen-switch.stackyard-docs.pages.dev

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