docs: the showcase documents vary their running heads

The book carries the chapter and the title towards the outer edge and its page
number centred at the foot; the newsletter opens with the masthead and runs a
head with a rule from the second page on. The thesis keeps chapter and number
in the head, so the three read as three page designs.

scripts/showcase/book.ts

@@ -59,12 +59,15 @@ export async function build(): Promise<Showcase> {
     ...body(raw),
   ] };
 
-  // Right-hand pages carry the chapter, left-hand pages the book; the number sits outside.
-  const right = HF({ tabStops: '11r' }, { type: 'chapterField', attrs: { level: 1, text: 'Down the Rabbit-Hole' } }, T('\t'), PAGE_NUMBER);
-  const left = HF({ tabStops: '11r' }, PAGE_NUMBER, T('\t'), T('Alice’s Adventures in Wonderland', ITALIC));
+  // Running heads name the chapter on right-hand pages, the book on left-hand ones, each
+  // towards the outer edge; the page number sits centred at the foot of every page.
+  const right = HF({ textAlign: 'right' }, { type: 'chapterField', attrs: { level: 1, text: 'Down the Rabbit-Hole' } });
+  const left = HF(null, T('Alice’s Adventures in Wonderland', ITALIC));
+  const folio = () => HF({ textAlign: 'center' }, PAGE_NUMBER);
   // A chapter opens on a right-hand page with no running head, its number at the foot.
   const chapterSet: HfSet = { ...EMPTY_HF_SET, header: right, headerEven: left, differentOddEven: true, startsOn: 'odd',
-    differentFirstPage: true, headerFirst: null, footerFirst: HF({ textAlign: 'center' }, PAGE_NUMBER) };
+    footer: folio(), footerEven: folio(),
+    differentFirstPage: true, headerFirst: null, footerFirst: folio() };
   const front: HfSet = { ...EMPTY_HF_SET };
   const sections = [front, ...Array.from({ length: 12 }, () => chapterSet)];
   sections[1] = { ...chapterSet, pageNumberStart: 1 };

scripts/showcase/newsletter.ts

@@ -102,13 +102,17 @@ export async function build(): Promise<Showcase> {
       T('Eden Astronomy Society, Oak Hill Observatory. Edited by the committee. Published four times a year. Contributions for the next issue to the editors by 15 November.', GREY, SMALL)),
   ] };
 
-  const footer = HF({ tabStops: '18r' }, T('Eden Astronomy Society  ·  Newsletter 3/2026', GREY, SMALL),
+  // The masthead is the first page's head; the pages after it carry a running one.
+  const header = HF({ tabStops: '18r', borderBottom: '0.5pt solid #5A6B7F', borderPadding: 2 },
+    T('Eden Astronomy Society', GREY, SMALL), T('\tSeptember 2026', GREY, SMALL));
+  const footer = () => HF({ tabStops: '18r' }, T('Newsletter 3/2026', GREY, SMALL),
     T('\tPage ', GREY, SMALL), PAGE_NUMBER);
 
   return {
     name: 'newsletter', doc, styles,
     margins: { top: 1.5, bottom: 1.5, left: 1.5, right: 1.5 },
-    hf: { header: null, footer, pageCount: 2, headerDistanceCm: 0.8, footerDistanceCm: 0.8 },
+    hf: { header, footer: footer(), headerFirst: null, footerFirst: footer(), differentFirstPage: true,
+      pageCount: 2, headerDistanceCm: 0.8, footerDistanceCm: 0.8 },
     language: { language: 'en', country: 'GB' },
     hyphenate: true,
     props: { title: 'Newsletter 3/2026', subject: 'Eden Astronomy Society', author: 'The committee', keywords: 'astronomy, society', description: '' },