Docs: sync widget copies for the books shelf redesign

[SandObserver]

Summary

• Refresh public/widgets/ and public/js/ from the app with npm run sync-widgets.
• The Books preview now shows the redesigned shelf: hairline shelf, serif spine titles, the book in progress named under the shelf, and a leaning last book on a sparse shelf.
• Every other synced file changes only its asset cache-busting stamps.

Testing
npm run build and npm run check pass. Checked the Books page on the production preview (port 4322) in Chrome, dark colour scheme, Auto theme.

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:	72cf62e
Status:	✅  Deploy successful!
Preview URL:	https://710ad0f3.stackyard-docs.pages.dev
Branch Preview URL:	https://docs-books-shelf-redesign.stackyard-docs.pages.dev

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