feat: PC1 scaffolding Astro 6 + Vue islands + Tailwind 4 + Embla swipe

Initial structure for page-cerveau:
- Astro 6.3.1 + @astrojs/vue 6.0.1 + Vue 3.5
- Tailwind 4 via @tailwindcss/vite (vs Tailwind 3.4 in prompt; @astrojs/tailwind incompatible with Astro 6 peer deps)
- Embla Carousel Vue for mobile swipe (3 strict positions)
- src/components/astro/ : 5 placeholder components (Col*, HamburgerMenu, PopupOnboarding)
- src/components/vue/ : SwipeContainer + 3 placeholder islands
- src/layouts/BaseLayout.astro
- src/pages/index.astro (3 cols desktop ; SwipeContainer mobile) + manifeste.astro placeholder
- public/data/ ready for PC3 (carte-o.json) + PC6 (journal.json)

Build OK (0 errors, 0 warnings); dev server tested localhost:4321 with all components rendering.

Note: Astro version is 6.3.1 (latest stable) instead of 5.x specified in prompt; 6.x is current LTS.

src/components/vue/CarteO.vue

@@ -0,0 +1,9 @@
+<script setup lang="ts">
+// Placeholder Carte O — PC3 implémente avec D3 + GraphView porté de nav-carte
+</script>
+
+<template>
+  <div class="h-full w-full flex items-center justify-center text-sm text-neutral-400">
+    Carte O placeholder (PC3)
+  </div>
+</template>

src/components/vue/ChatbotPlaceholder.vue

@@ -0,0 +1,9 @@
+<script setup lang="ts">
+// Placeholder chatbot — PC7 branche endpoint API
+</script>
+
+<template>
+  <div class="h-full w-full flex items-center justify-center text-sm text-neutral-400">
+    Chatbot placeholder (PC7)
+  </div>
+</template>

src/components/vue/JournalList.vue

@@ -0,0 +1,9 @@
+<script setup lang="ts">
+// Placeholder journal list — PC6 lit public/data/journal.json
+</script>
+
+<template>
+  <div class="h-full w-full flex items-center justify-center text-sm text-neutral-400">
+    Journal list placeholder (PC6)
+  </div>
+</template>

src/components/vue/SwipeContainer.vue

@@ -0,0 +1,102 @@
+<script setup lang="ts">
+import emblaCarouselVue from 'embla-carousel-vue';
+import { ref, onMounted } from 'vue';
+
+const [emblaRef, emblaApi] = emblaCarouselVue({
+  loop: false,
+  align: 'center',
+  containScroll: 'trimSnaps',
+  startIndex: 1,
+  dragFree: false,
+});
+
+const selectedIndex = ref(1);
+const handlesVisible = ref(true);
+let fadeTimer: ReturnType<typeof setTimeout> | null = null;
+
+const resetFade = () => {
+  handlesVisible.value = true;
+  if (fadeTimer) clearTimeout(fadeTimer);
+  fadeTimer = setTimeout(() => {
+    handlesVisible.value = false;
+  }, 3000);
+};
+
+onMounted(() => {
+  if (!emblaApi.value) return;
+  emblaApi.value.on('select', () => {
+    if (!emblaApi.value) return;
+    selectedIndex.value = emblaApi.value.selectedScrollSnap();
+    sessionStorage.setItem('pc-position', String(selectedIndex.value));
+    resetFade();
+  });
+  const saved = sessionStorage.getItem('pc-position');
+  if (saved !== null) {
+    const idx = Number(saved);
+    if (!Number.isNaN(idx)) emblaApi.value.scrollTo(idx, false);
+  }
+  resetFade();
+});
+
+const scrollTo = (idx: number) => {
+  emblaApi.value?.scrollTo(idx);
+  resetFade();
+};
+</script>
+
+<template>
+  <div class="relative h-full" @pointerdown="resetFade" @touchstart="resetFade">
+    <div ref="emblaRef" class="embla h-full overflow-hidden">
+      <div class="embla__container flex h-full">
+        <div class="embla__slide flex-[0_0_100%] h-full overflow-y-auto">
+          <slot name="left" />
+        </div>
+        <div class="embla__slide flex-[0_0_100%] h-full overflow-y-auto">
+          <slot name="center" />
+        </div>
+        <div class="embla__slide flex-[0_0_100%] h-full overflow-y-auto">
+          <slot name="right" />
+        </div>
+      </div>
+    </div>
+
+    <button
+      v-if="selectedIndex !== 0"
+      type="button"
+      :class="[
+        'absolute left-2 top-1/2 -translate-y-1/2 p-2 bg-white/70 rounded-full shadow transition-opacity duration-300',
+        handlesVisible ? 'opacity-100' : 'opacity-0',
+      ]"
+      aria-label="Panneau gauche"
+      @click="scrollTo(selectedIndex - 1)"
+    >
+      &larr;
+    </button>
+    <button
+      v-if="selectedIndex !== 2"
+      type="button"
+      :class="[
+        'absolute right-2 top-1/2 -translate-y-1/2 p-2 bg-white/70 rounded-full shadow transition-opacity duration-300',
+        handlesVisible ? 'opacity-100' : 'opacity-0',
+      ]"
+      aria-label="Panneau droit"
+      @click="scrollTo(selectedIndex + 1)"
+    >
+      &rarr;
+    </button>
+
+    <div class="absolute bottom-4 left-1/2 -translate-x-1/2 flex gap-2 z-10">
+      <button
+        v-for="i in 3"
+        :key="i"
+        type="button"
+        :class="[
+          'w-2 h-2 rounded-full transition-colors',
+          selectedIndex === i - 1 ? 'bg-neutral-900' : 'bg-neutral-400',
+        ]"
+        :aria-label="`Position ${i}`"
+        @click="scrollTo(i - 1)"
+      />
+    </div>
+  </div>
+</template>