feat(glossary): add step 21 smart navigation

src/components/SiteNav.astro

@@ -1,15 +1,24 @@
+---
+const path = Astro.url.pathname;
+
+const isActive = (href: string) => {
+  if (href === "/") return path === "/";
+  return path === href || path.startsWith(href);
+};
+---
+
 <nav class="site-nav" aria-label="Navigation principale">
-  <a href="/">Accueil</a>
+  <a href="/" aria-current={isActive("/") ? "page" : undefined}>Accueil</a>
   <span aria-hidden="true"> · </span>
 
-  <a href="/archicrat-ia/">Essai-thèse — ArchiCraT-IA</a>
+  <a href="/archicrat-ia/" aria-current={isActive("/archicrat-ia/") ? "page" : undefined}>Essai-thèse — ArchiCraT-IA</a>
   <span aria-hidden="true"> · </span>
 
-  <a href="/cas-ia/">Cas pratique — Gouvernance IA</a>
+  <a href="/cas-ia/" aria-current={isActive("/cas-ia/") ? "page" : undefined}>Cas pratique — Gouvernance IA</a>
   <span aria-hidden="true"> · </span>
 
-  <a href="/glossaire/">Glossaire</a>
+  <a href="/glossaire/" aria-current={isActive("/glossaire/") ? "page" : undefined}>Glossaire</a>
   <span aria-hidden="true"> · </span>
 
-  <a href="/recherche/">Recherche</a>
+  <a href="/recherche/" aria-current={isActive("/recherche/") ? "page" : undefined}>Recherche</a>
 </nav>