feat(06-04): add BlogToc component (sticky desktop + drawer mobile + IntersectionObserver highlight)

app/components/BlogToc.vue

@@ -0,0 +1,158 @@
+<script setup lang="ts">
+interface TocLink {
+  id: string
+  depth: number
+  text: string
+  children?: TocLink[]
+}
+
+interface Props {
+  links: TocLink[]
+}
+
+const props = defineProps<Props>()
+const { t } = useI18n()
+
+const drawerOpen = ref(false)
+const activeId = ref<string | null>(null)
+let observer: IntersectionObserver | null = null
+
+const flatIds = computed(() => {
+  const ids: string[] = []
+  const collect = (nodes: TocLink[]) => {
+    for (const node of nodes) {
+      ids.push(node.id)
+      if (node.children?.length) collect(node.children)
+    }
+  }
+  collect(props.links)
+  return ids
+})
+
+onMounted(() => {
+  if (typeof window === 'undefined') return
+
+  activeId.value = flatIds.value[0] ?? null
+
+  observer = new IntersectionObserver(
+    (entries) => {
+      const visible = entries
+        .filter((e) => e.isIntersecting)
+        .sort((a, b) => a.target.getBoundingClientRect().top - b.target.getBoundingClientRect().top)
+      if (visible.length > 0) {
+        activeId.value = visible[0]!.target.id
+      }
+    },
+    { rootMargin: '-20% 0px -70% 0px', threshold: 0 },
+  )
+
+  for (const id of flatIds.value) {
+    const el = document.getElementById(id)
+    if (el) observer.observe(el)
+  }
+})
+
+onBeforeUnmount(() => {
+  observer?.disconnect()
+  observer = null
+})
+
+function handleItemClick() {
+  drawerOpen.value = false
+}
+</script>
+
+<template>
+  <!-- Desktop sticky sidebar -->
+  <aside class="hidden lg:block sticky top-24 w-64 self-start">
+    <p class="text-sm font-bold uppercase tracking-wider text-gray-500 dark:text-gray-400 mb-4">
+      {{ t('blog.toc.title') }}
+    </p>
+    <ol class="space-y-2 text-sm">
+      <li v-for="link in links" :key="link.id">
+        <a
+          :href="`#${link.id}`"
+          :class="[
+            activeId === link.id
+              ? 'text-brand-500 dark:text-brand-400 font-medium'
+              : 'text-gray-500 dark:text-gray-400 hover:text-gray-900 dark:hover:text-white',
+            'block transition-colors',
+          ]"
+        >
+          {{ link.text }}
+        </a>
+        <ol v-if="link.children?.length" class="mt-1 ml-4 space-y-1">
+          <li v-for="child in link.children" :key="child.id">
+            <a
+              :href="`#${child.id}`"
+              :class="[
+                activeId === child.id
+                  ? 'text-brand-500 dark:text-brand-400 font-medium'
+                  : 'text-gray-500 dark:text-gray-400 hover:text-gray-900 dark:hover:text-white',
+                'block transition-colors',
+              ]"
+            >
+              {{ child.text }}
+            </a>
+          </li>
+        </ol>
+      </li>
+    </ol>
+  </aside>
+
+  <!-- Mobile trigger + drawer -->
+  <div class="lg:hidden inline-block">
+    <UButton
+      variant="ghost"
+      color="neutral"
+      size="sm"
+      icon="i-lucide-list"
+      :aria-label="t('a11y.blogTocToggle')"
+      @click="drawerOpen = true"
+    >
+      {{ t('blog.toc.title') }}
+    </UButton>
+
+    <UDrawer v-model:open="drawerOpen" direction="right">
+      <template #header>
+        <p class="text-sm font-bold uppercase tracking-wider text-gray-500 dark:text-gray-400">
+          {{ t('blog.toc.title') }}
+        </p>
+      </template>
+      <template #body>
+        <ol class="space-y-3 text-sm p-4">
+          <li v-for="link in links" :key="link.id">
+            <a
+              :href="`#${link.id}`"
+              :class="[
+                activeId === link.id
+                  ? 'text-brand-500 dark:text-brand-400 font-medium'
+                  : 'text-gray-600 dark:text-gray-300',
+                'block transition-colors',
+              ]"
+              @click="handleItemClick"
+            >
+              {{ link.text }}
+            </a>
+            <ol v-if="link.children?.length" class="mt-2 ml-4 space-y-2">
+              <li v-for="child in link.children" :key="child.id">
+                <a
+                  :href="`#${child.id}`"
+                  :class="[
+                    activeId === child.id
+                      ? 'text-brand-500 dark:text-brand-400 font-medium'
+                      : 'text-gray-500 dark:text-gray-400',
+                    'block transition-colors',
+                  ]"
+                  @click="handleItemClick"
+                >
+                  {{ child.text }}
+                </a>
+              </li>
+            </ol>
+          </li>
+        </ol>
+      </template>
+    </UDrawer>
+  </div>
+</template>