fix(a11y): fix WCAG AA contrast and WCAG 2.5.3 failures from third report

- css/tailwind.css: upgrade nav/mobile-nav/theme-toggle text from
  surface-600 (fails 4.5:1) to surface-700 across .site-nav, .nav-dropdown-menu,
  .menu-toggle, .mobile-nav, .mobile-nav-toggle, .theme-toggle, .mobile-theme-toggle
- post.njk: fix AI disclosure details and 'Also on:' span to surface-700
- webmentions.njk: fix summary to surface-700; fix Send button from
  bg-accent-600 (3.18:1) to bg-accent-700 (4.95:1)
- h-card.njk: fix p-adr address and PGP key link to surface-700
- base.njk: fix mobile theme toggle aria-label per WCAG 2.5.3
- post-categories.njk: fix category pills text-accent-700 to text-accent-800
- post-navigation.njk: fix no-OG fallback Previous/Next labels to surface-700

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

_includes/components/h-card.njk

@@ -47,7 +47,7 @@
       <p class="p-job-title text-sm text-surface-600 dark:text-surface-400" itemprop="jobTitle">{{ authorTitle }}</p>
       {% endif %}
       {# Structured address #}
-      <p class="p-adr h-adr text-sm text-surface-600 dark:text-surface-400" itemprop="address" itemscope itemtype="http://schema.org/PostalAddress">
+      <p class="p-adr h-adr text-sm text-surface-700 dark:text-surface-300" itemprop="address" itemscope itemtype="http://schema.org/PostalAddress">
         {% if authorLocality %}
         <span class="p-locality" itemprop="addressLocality">{{ authorLocality }}</span>{% if authorCountry %}, {% endif %}
         {% endif %}
@@ -83,7 +83,7 @@
     </a>
     {% endif %}
     {% if authorKeyUrl %}
-    <a href="{{ authorKeyUrl }}" class="u-key text-surface-600 dark:text-surface-400 hover:underline" rel="pgpkey">
+    <a href="{{ authorKeyUrl }}" class="u-key text-surface-700 dark:text-surface-300 hover:underline" rel="pgpkey">
       🔐 PGP Key
     </a>
     {% endif %}

_includes/components/post-navigation.njk

@@ -39,7 +39,7 @@
       </span>
       {% else %}
       <div class="p-4 sm:p-5">
-        <span class="text-[10px] sm:text-xs font-semibold uppercase tracking-wide text-surface-600 dark:text-surface-400 block mb-2">&larr; Previous</span>
+        <span class="text-[10px] sm:text-xs font-semibold uppercase tracking-wide text-surface-700 dark:text-surface-300 block mb-2">&larr; Previous</span>
         <span class="text-sm sm:text-base font-medium text-surface-900 dark:text-surface-100 group-hover:text-accent-700 dark:group-hover:text-accent-300 line-clamp-2 transition-colors">
           {{ _prevTitle }}
         </span>
@@ -85,7 +85,7 @@
       </span>
       {% else %}
       <div class="p-4 sm:p-5 text-right">
-        <span class="text-[10px] sm:text-xs font-semibold uppercase tracking-wide text-surface-600 dark:text-surface-400 block mb-2">Next &rarr;</span>
+        <span class="text-[10px] sm:text-xs font-semibold uppercase tracking-wide text-surface-700 dark:text-surface-300 block mb-2">Next &rarr;</span>
         <span class="text-sm sm:text-base font-medium text-surface-900 dark:text-surface-100 group-hover:text-accent-700 dark:group-hover:text-accent-300 line-clamp-2 transition-colors">
           {{ _nextTitle }}
         </span>

_includes/components/webmentions.njk

@@ -183,7 +183,7 @@
 
 {# Webmention send form — collapsed by default #}
 <details class="mt-8">
-  <summary class="text-sm font-semibold text-surface-600 dark:text-surface-400 cursor-pointer hover:text-surface-700 dark:hover:text-surface-300 transition-colors list-none [&::-webkit-details-marker]:hidden flex items-center gap-1.5">
+  <summary class="text-sm font-semibold text-surface-700 dark:text-surface-300 cursor-pointer hover:text-surface-800 dark:hover:text-surface-200 transition-colors list-none [&::-webkit-details-marker]:hidden flex items-center gap-1.5">
     <svg class="w-3.5 h-3.5 transition-transform [[open]>&]:rotate-90" fill="none" stroke="currentColor" viewBox="0 0 24 24" aria-hidden="true">
       <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 5l7 7-7 7"/>
     </svg>
@@ -206,7 +206,7 @@
       >
       <button
         type="submit"
-        class="px-4 py-2 text-sm font-medium text-white bg-accent-600 hover:bg-accent-700 rounded transition-colors">
+        class="px-4 py-2 text-sm font-medium text-white bg-accent-700 hover:bg-accent-800 rounded transition-colors">
         Send
       </button>
     </form>

_includes/components/widgets/post-categories.njk

@@ -5,12 +5,12 @@
   <h3 class="widget-title">Categories</h3>
   <div class="flex flex-wrap gap-2">
     {% if category is string %}
-    <a href="/categories/{{ category | slugify }}/" class="p-category text-xs px-2 py-1 bg-accent-100 dark:bg-accent-900/30 text-accent-700 dark:text-accent-300 rounded-full hover:bg-accent-200 dark:hover:bg-accent-800 transition-colors">
+    <a href="/categories/{{ category | slugify }}/" class="p-category text-xs px-2 py-1 bg-accent-100 dark:bg-accent-900/30 text-accent-800 dark:text-accent-300 rounded-full hover:bg-accent-200 dark:hover:bg-accent-800 transition-colors">
       {{ category }}
     </a>
     {% else %}
     {% for cat in category %}
-    <a href="/categories/{{ cat | slugify }}/" class="p-category text-xs px-2 py-1 bg-accent-100 dark:bg-accent-900/30 text-accent-700 dark:text-accent-300 rounded-full hover:bg-accent-200 dark:hover:bg-accent-800 transition-colors">
+    <a href="/categories/{{ cat | slugify }}/" class="p-category text-xs px-2 py-1 bg-accent-100 dark:bg-accent-900/30 text-accent-800 dark:text-accent-300 rounded-full hover:bg-accent-200 dark:hover:bg-accent-800 transition-colors">
       {{ cat }}
     </a>
     {% endfor %}

_includes/layouts/base.njk

@@ -268,7 +268,7 @@
         Dashboard
       </a>
       {# Mobile theme toggle #}
-      <button type="button" class="mobile-theme-toggle" aria-label="Toggle dark mode">
+      <button type="button" class="mobile-theme-toggle" aria-label="Theme: toggle dark mode">
         <span class="theme-label">Theme</span>
         <span class="theme-icons">
           <svg class="sun-icon" width="20" height="20" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" aria-hidden="true">

_includes/layouts/post.njk

@@ -78,8 +78,8 @@ withBlogSidebar: true
 
   {# AI usage disclosure — articles and notes only #}
   {% if '/articles/' in page.url or '/notes/' in page.url %}
-  <details class="mt-4 text-xs text-surface-600 dark:text-surface-400">
+  <details class="mt-4 text-xs text-surface-700 dark:text-surface-300">
-    <summary class="cursor-pointer hover:text-surface-600 dark:hover:text-surface-300 list-none flex items-center gap-1.5 [&::-webkit-details-marker]:hidden">
+    <summary class="cursor-pointer hover:text-surface-700 dark:hover:text-surface-200 list-none flex items-center gap-1.5 [&::-webkit-details-marker]:hidden">
       <svg class="w-3.5 h-3.5 flex-shrink-0" fill="none" stroke="currentColor" viewBox="0 0 24 24" aria-hidden="true">
         <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9.75 3.104v5.714a2.25 2.25 0 01-.659 1.591L5 14.5M9.75 3.104c-.251.023-.501.05-.75.082m.75-.082a24.301 24.301 0 014.5 0m0 0v5.714a2.25 2.25 0 00.659 1.591L19 14.5M14.25 3.104c.251.023.501.05.75.082M19 14.5l-2.47 2.47a2.25 2.25 0 01-1.59.659H9.06a2.25 2.25 0 01-1.591-.659L5 14.5m14 0V17a2 2 0 01-2 2H7a2 2 0 01-2-2v-2.5"/>
       </svg>
@@ -131,7 +131,7 @@ withBlogSidebar: true
   {% if externalSyndication.length or selfHostedApUrl %}
   <footer class="post-footer mt-8 pt-6 border-t border-surface-200 dark:border-surface-700">
     <div class="flex flex-wrap items-center gap-4">
-      <span class="text-sm text-surface-600 dark:text-surface-400">Also on:</span>
+      <span class="text-sm text-surface-700 dark:text-surface-300">Also on:</span>
       <div class="flex flex-wrap gap-3">
         {# Fediverse remote interaction button (self-hosted ActivityPub) #}
         {% if selfHostedApUrl %}

css/tailwind.css

@@ -168,7 +168,7 @@
 
   .site-nav > a,
   .site-nav .nav-dropdown-trigger {
-    @apply text-surface-600 dark:text-surface-400 hover:text-surface-900 dark:hover:text-surface-100 no-underline transition-colors py-2;
+    @apply text-surface-700 dark:text-surface-300 hover:text-surface-900 dark:hover:text-surface-100 no-underline transition-colors py-2;
   }
 
   /* Navigation dropdown */
@@ -187,7 +187,7 @@
   }
 
   .nav-dropdown-menu a {
-    @apply block px-4 py-2.5 text-sm text-surface-600 dark:text-surface-400 hover:bg-surface-100 dark:hover:bg-surface-700 hover:text-surface-900 dark:hover:text-surface-100 no-underline;
+    @apply block px-4 py-2.5 text-sm text-surface-700 dark:text-surface-300 hover:bg-surface-100 dark:hover:bg-surface-700 hover:text-surface-900 dark:hover:text-surface-100 no-underline;
   }
 
   .nav-dropdown-divider {
@@ -196,7 +196,7 @@
 
   /* Mobile menu toggle button */
   .menu-toggle {
-    @apply md:hidden p-2 rounded-lg text-surface-600 dark:text-surface-400 hover:bg-surface-100 dark:hover:bg-surface-800 transition-colors;
+    @apply md:hidden p-2 rounded-lg text-surface-700 dark:text-surface-300 hover:bg-surface-100 dark:hover:bg-surface-800 transition-colors;
   }
 
   /* Mobile navigation dropdown */
@@ -207,7 +207,7 @@
   }
 
   .mobile-nav a {
-    @apply block px-4 py-3 text-surface-600 dark:text-surface-400 hover:bg-surface-100 dark:hover:bg-surface-800 hover:text-surface-900 dark:hover:text-surface-100 no-underline transition-colors border-b border-surface-100 dark:border-surface-800 last:border-b-0;
+    @apply block px-4 py-3 text-surface-700 dark:text-surface-300 hover:bg-surface-100 dark:hover:bg-surface-800 hover:text-surface-900 dark:hover:text-surface-100 no-underline transition-colors border-b border-surface-100 dark:border-surface-800 last:border-b-0;
   }
 
   /* Mobile nav collapsible sections */
@@ -216,7 +216,7 @@
   }
 
   .mobile-nav-toggle {
-    @apply flex items-center justify-between w-full px-4 py-3 text-surface-600 dark:text-surface-400 hover:bg-surface-100 dark:hover:bg-surface-800 hover:text-surface-900 dark:hover:text-surface-100 transition-colors bg-transparent border-none text-base text-left cursor-pointer;
+    @apply flex items-center justify-between w-full px-4 py-3 text-surface-700 dark:text-surface-300 hover:bg-surface-100 dark:hover:bg-surface-800 hover:text-surface-900 dark:hover:text-surface-100 transition-colors bg-transparent border-none text-base text-left cursor-pointer;
   }
 
   .mobile-nav-submenu {
@@ -233,7 +233,7 @@
 
   /* Theme toggle button */
   .theme-toggle {
-    @apply p-2 rounded-lg text-surface-600 dark:text-surface-400 hover:bg-surface-100 dark:hover:bg-surface-800 transition-colors;
+    @apply p-2 rounded-lg text-surface-700 dark:text-surface-300 hover:bg-surface-100 dark:hover:bg-surface-800 transition-colors;
   }
 
   .theme-toggle .sun-icon {
@@ -254,7 +254,7 @@
 
   /* Mobile theme toggle */
   .mobile-theme-toggle {
-    @apply flex items-center justify-between w-full px-4 py-3 text-surface-600 dark:text-surface-400 hover:bg-surface-100 dark:hover:bg-surface-800 hover:text-surface-900 dark:hover:text-surface-100 transition-colors bg-transparent border-none text-base text-left cursor-pointer border-t border-surface-200 dark:border-surface-700;
+    @apply flex items-center justify-between w-full px-4 py-3 text-surface-700 dark:text-surface-300 hover:bg-surface-100 dark:hover:bg-surface-800 hover:text-surface-900 dark:hover:text-surface-100 transition-colors bg-transparent border-none text-base text-left cursor-pointer border-t border-surface-200 dark:border-surface-700;
   }
 
   .mobile-theme-toggle .theme-label {