feat(web): adopt Gov.uk design patterns — typography + print button (#122)

Typography (Gov.uk accessibility research):
- Line-height: 1.7 → 1.5 (Gov.uk uses 1.32, legal docs typically 1.5)
- Mobile font: remove 16px override, keep 19px everywhere
  (Gov.uk finding: smaller mobile fonts hurt accessibility)

Print button:
- Add "Print" button to section metadata bar
- Uses window.print() with existing print stylesheet
- Legal researchers routinely print statute sections

Based on Gov.uk Design System and legislation.gov.uk research.
Consensus approved 2-0.

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: williamzujkowski

apps/web/src/pages/statute/[...slug].astro

@@ -148,6 +148,13 @@ const readingTimeMin = Math.max(1, Math.round(wordCount / 200));
       >
         View on OLRC →
       </a>
+      <button
+        onclick="window.print()"
+        class="rounded bg-gray-100 px-2 py-1 text-gray-600 hover:bg-gray-200 transition-colors dark:bg-gray-800 dark:text-gray-400 dark:hover:bg-gray-700"
+        aria-label="Print this section"
+      >
+        Print
+      </button>
     </div>
   </div>
 

apps/web/src/styles/global.css

@@ -16,7 +16,7 @@
 /* Legal text readability — 19px desktop, 16px mobile */
 .prose {
   font-size: 1.1875rem; /* 19px — optimal for legal text readability */
-  line-height: 1.7; /* Wikipedia research: 1.4-1.7 optimal for reading speed + comprehension */
+  line-height: 1.5; /* Gov.uk uses 1.32 (25/19px), legal docs use 1.5 — balances density + readability */
   max-width: min(72ch, 100%);
 }
 
@@ -120,16 +120,11 @@
   border-color: var(--color-gray-700, #334155);
 }
 
-/* Mobile prose — tighter width, smaller font, more spacing for thumb-scrolling */
+/* Mobile prose — tighter width, keep 19px font (Gov.uk accessibility: same size all screens) */
 @media (max-width: 768px) {
   .prose {
-    font-size: 1rem; /* 16px on mobile */
     max-width: min(90vw, 65ch);
   }
-  .prose p {
-    margin-top: 1.5em;
-    margin-bottom: 1.5em;
-  }
 }
 
 /* Sticky section headers on chapter pages — shows which section user is reading */