Offer the manual as PDF and EPUB, laid out for print

The page gains a print stylesheet: A4 with a cover, a contents page whose
entries carry their page numbers, a chapter to a page with its name at the
head of each page and the page count at the foot, figures and table rows
never split, and the light palette. A line above the title links the PDF
and the EPUB on the published site, absolutely, since an installed copy
has none beside it.

The Manual pages workflow makes both: tools/manual/pdf.py renders the page
with WeasyPrint from JPEG copies of its pictures, which takes the PDF from
28 MB to 8, and pandoc makes the EPUB from the Markdown.

docs/manual/index.html

@@ -90,15 +90,50 @@ figcaption { margin-top: 0.4rem; color: var(--ink-dim); font-size: 0.9rem; }
 table { border-collapse: collapse; width: 100%; font-size: 0.95rem; }
 th, td { text-align: left; padding: 0.4rem 0.6rem; border-bottom: 1px solid var(--rule); vertical-align: top; }
 th { color: var(--ink-dim); font-weight: 600; }
+td img { aspect-ratio: auto 1 / 1; }
+.downloads { margin: 0 0 1.2rem; color: var(--ink-dim); font-size: 0.9rem; }
+.cover { display: none; }
 @media (max-width: 52rem) {
   .page { grid-template-columns: minmax(0, 1fr); gap: 1rem; padding: 1rem 16px 3rem; }
   .toc { position: static; max-height: none; border: 1px solid var(--rule); border-radius: 6px; padding: 0.8rem 1rem; background: var(--panel); }
   body { font-size: 16px; }
 }
+@page {
+  size: A4;
+  margin: 18mm 16mm 20mm;
+  @top-right { content: string(chapter); font: 8.5pt system-ui, sans-serif; color: #5c5955; }
+  @bottom-center { content: counter(page) " / " counter(pages); font: 8.5pt system-ui, sans-serif; color: #5c5955; }
+}
+@page :first { @top-right { content: none; } @bottom-center { content: none; } }
+@media print {
+  :root { --bg: #fff; --ink: #1d1c1a; --ink-dim: #5c5955; --rule: #dedad4; --accent: #8a4b12; --panel: #f1eee9; --mark: transparent; }
+  body { font-size: 10.5pt; line-height: 1.5; }
+  .page { display: block; padding: 0; }
+  .downloads { display: none; }
+  .cover { display: block; break-after: page; padding-top: 80mm; }
+  .cover-title { font-size: 34pt; font-weight: 700; margin: 0 0 6mm; }
+  .cover-sub { color: var(--ink-dim); margin: 0; }
+  .toc { position: static; max-height: none; overflow: visible; break-after: page; font-size: 10pt; }
+  .toc-title { font-size: 9pt; }
+  .toc a { color: var(--ink); }
+  .toc a::after { content: leader('.') target-counter(attr(href), page); color: var(--ink-dim); }
+  .toc ul ul a { color: var(--ink-dim); }
+  main { display: contents; }
+  h1 { font-size: 24pt; }
+  h2 { break-before: page; border-top: none; padding-top: 0; margin-top: 0; string-set: chapter content(); }
+  h2, h3 { break-after: avoid; }
+  figure, tr, img { break-inside: avoid; }
+  figure img, main img { max-height: 100mm; width: auto; max-width: 100%; margin: 0 auto; }
+  figure { margin: 4mm 0; }
+  td img { max-height: 60mm; }
+  a { color: inherit; text-decoration: none; }
+  p, li { orphans: 3; widows: 3; }
+}
 </style>
 </head>
 <body>
 <div class="page">
+<header class="cover"><p class="cover-title">DarkRoom, shown</p><p class="cover-sub">The DarkRoom manual · https://pages.tourolle.paris/dtourolle/darkroom/</p></header>
 <nav class="toc" aria-label="Contents">
 <p class="toc-title">Contents</p>
 <ul>
@@ -137,6 +172,7 @@ th { color: var(--ink-dim); font-weight: 600; }
 </ul>
 </nav>
 <main>
+<p class="downloads">Also as <a href="https://pages.tourolle.paris/dtourolle/darkroom/darkroom-manual.pdf" download>PDF</a> · <a href="https://pages.tourolle.paris/dtourolle/darkroom/darkroom-manual.epub" download>EPUB</a> · <a href="https://pages.tourolle.paris/dtourolle/darkroom/">online</a></p>
 <h1 id="darkroom-shown">DarkRoom, shown</h1>
 <p>A tour of what the application does, one picture per thing. Every image on
 this page was captured from the desktop build driving itself — nothing is a