feat(css): add :target highlighting for anchor navigation

- Highlight heading with accent border-left when targeted via URL hash
- Show pilcrow anchor visibly on targeted headings
- Add scroll-margin-top for better scroll positioning

docs/static/style.css

@@ -218,6 +218,29 @@ h6:hover .heading-anchor {
   visibility: visible;
 }
 
+/* Highlight heading when :target (clicked anchor) */
+h1:target,
+h2:target,
+h3:target,
+h4:target,
+h5:target,
+h6:target {
+  scroll-margin-top: 1rem;
+  padding-left: 0.5rem;
+  border-left: 3px solid var(--accent);
+}
+
+/* Always show pilcrow on targeted heading */
+h1:target .heading-anchor,
+h2:target .heading-anchor,
+h3:target .heading-anchor,
+h4:target .heading-anchor,
+h5:target .heading-anchor,
+h6:target .heading-anchor {
+  visibility: visible;
+  color: var(--accent);
+}
+
 p {
   margin-bottom: 1rem;
 }
@@ -588,4 +611,4 @@ th {
   td code {
     white-space: normal;
   }
-}
+}