fix(nav): show all 5 items on narrow screens (n+6 cap) and scope active state per page (#19)

Author: patterncatalyst

_includes/header.html

@@ -6,8 +6,9 @@
     </a>
     <nav class="site-nav" aria-label="Primary">
       <a href="{{ '/docs/00-index/' | relative_url }}"
-         {% if page.url contains '/docs/' %}aria-current="page"{% endif %}>Contents</a>
-      <a href="{{ '/docs/10-summary/' | relative_url }}">Summary</a>
+         {% if page.url == '/docs/00-index/' %}aria-current="page"{% endif %}>Contents</a>
+      <a href="{{ '/docs/10-summary/' | relative_url }}"
+         {% if page.url == '/docs/10-summary/' %}aria-current="page"{% endif %}>Summary</a>
       <a href="{{ '/demos/' | relative_url }}"
          {% if page.url == '/demos/' or page.url == '/setup/' %}aria-current="page"{% endif %}>Demos</a>
       <a href="{{ '/bibliography/' | relative_url }}"

assets/css/site.css

@@ -274,7 +274,7 @@ pre code {
 @media (max-width: 720px) {
   .site-header__inner { height: 3.5rem; gap: var(--space-3); }
   .site-nav { gap: var(--space-3); font-size: .875rem; }
-  .site-nav a:nth-child(n+5) { display: none; }
+  .site-nav a:nth-child(n+6) { display: none; }
 }
 
 /* ---- 6. Hero ----------------------------------------------- */