docs: the book spread shows a chapter opening beside a running page

The shot follows the chapter heading rather than a fixed page, so it keeps both
page designs in view if the break ever moves. The gallery notes why the folio
and the document page differ there.

README.md

@@ -72,7 +72,7 @@ both public domain.
 
 | | |
 |---|---|
-| [![Tracked changes and comments](docs/showcase/thesis-review.png)](docs/showcase/thesis-review.png) **Review** — tracked changes, threaded comments in the margin, a draft watermark | [![A book on facing pages](docs/showcase/book-spread.png)](docs/showcase/book-spread.png) **Book** — A5, mirrored margins, chapters opening on a right-hand page, running heads |
+| [![Tracked changes and comments](docs/showcase/thesis-review.png)](docs/showcase/thesis-review.png) **Review** — tracked changes, threaded comments in the margin, a draft watermark | [![A book on facing pages](docs/showcase/book-spread.png)](docs/showcase/book-spread.png) **Book** — A5, mirrored margins, chapters opening on a right-hand page, running heads; the numbering restarts after the front matter, so page 11 prints the folio 9 |
 | [![A newsletter in two columns](docs/showcase/newsletter.png)](docs/showcase/newsletter.png) **Newsletter** — columns, pictures with captions, a sidebar box | [![Tables with formulas](docs/showcase/newsletter-tables.png)](docs/showcase/newsletter-tables.png) **Tables** — table styles and spreadsheet-style formulas |
 
 ## Development

scripts/showcase/book.ts

@@ -82,7 +82,8 @@ export async function build(): Promise<Showcase> {
     props: { title: 'Alice’s Adventures in Wonderland', subject: '', author: 'Lewis Carroll', keywords: '', description: '' },
     shots: [
       { file: 'book', page: 3 },
-      { file: 'book-spread', page: 3, columns: 2, tab: 'layout' },
+      // The spread that shows both page designs: a chapter opening beside a running one.
+      { file: 'book-spread', at: 'The Pool of Tears', columns: 2, tab: 'layout' },
     ],
   };
 }