feat: add responsive professional information layer

src/components/SiteNavigation.vue

@@ -5,7 +5,7 @@ defineProps<{ items: ReadonlyArray<{ id: SectionId; label: string }> }>();
 </script>
 
 <template>
-  <nav aria-label="Portfolio sections">
+  <nav class="site-navigation" aria-label="Portfolio sections">
     <ul>
       <li v-for="item in items" :key="item.id">
         <a :href="`#${item.id}`">{{ item.label }}</a>