feat(pc2): hamburger nav + manifeste V1 + popup onboarding

- HamburgerMenu drawer slide-in left avec liens A propos, Manifeste, Mentions legales (ESC + clic overlay pour fermer)
- ColJournal enrichi : CTA Manifeste, accordeon Hashtags (7 plateformes, ferme mobile / ouvert desktop, persistence localStorage), skeleton Journal pour PC6
- Page /manifeste : V1 redige integre (em-dashes remplaces par tirets/points-virgules), pivot stylise blockquote, diagramme mouvements en 3 sections boites
- Page /manifeste/commander : stub form pre-inscription (V1 localStorage, V1.1 cable Listmonk)
- Page /a-propos : extrait de Contexte Global, 3-4 paragraphes Jules
- Page /mentions-legales : placeholder court (editeur, hebergeur Hetzner, pas de cookies)
- PopupOnboarding : micro-resume 3 lignes proposees, dismiss X / CTA / scroll 200px / ESC, flag tf-onboarded

src/components/astro/HamburgerMenu.astro

@@ -1,12 +1,103 @@
 ---
-// Placeholder hamburger menu — PC2 ajoute liens nav
+// HamburgerMenu - drawer slide-in left avec liens nav (PC2)
+// Astro vanilla + script inline, pas besoin d'island Vue
 ---
 <button
+  id="hamburger-trigger"
   type="button"
-  class="fixed top-3 right-3 z-30 p-2 rounded bg-white/80 border border-neutral-200 shadow-sm"
-  aria-label="Menu"
+  class="fixed top-4 left-4 z-50 p-3 bg-white/95 border border-neutral-200 rounded-lg shadow-md hover:bg-white transition-colors md:top-6 md:left-6"
+  aria-label="Ouvrir le menu"
+  aria-expanded="false"
+  aria-controls="hamburger-drawer"
 >
-  <span class="block w-5 h-0.5 bg-neutral-700 mb-1"></span>
-  <span class="block w-5 h-0.5 bg-neutral-700 mb-1"></span>
-  <span class="block w-5 h-0.5 bg-neutral-700"></span>
+  <span class="block w-5 h-0.5 bg-neutral-800 mb-1"></span>
+  <span class="block w-5 h-0.5 bg-neutral-800 mb-1"></span>
+  <span class="block w-5 h-0.5 bg-neutral-800"></span>
 </button>
+
+<div
+  id="hamburger-drawer"
+  class="fixed inset-0 z-40 hidden"
+  role="dialog"
+  aria-modal="true"
+  aria-label="Menu de navigation"
+>
+  <div
+    class="absolute inset-0 bg-black/30 transition-opacity"
+    data-drawer-close
+    aria-hidden="true"
+  ></div>
+  <nav
+    id="hamburger-nav"
+    class="absolute left-0 top-0 h-full w-72 max-w-[80vw] bg-white shadow-xl p-6 transform -translate-x-full transition-transform duration-200 ease-out"
+  >
+    <button
+      type="button"
+      data-drawer-close
+      class="absolute top-4 right-4 w-9 h-9 flex items-center justify-center text-neutral-500 hover:text-neutral-900 text-2xl leading-none rounded-md hover:bg-neutral-100"
+      aria-label="Fermer le menu"
+    >
+      &times;
+    </button>
+    <ul class="mt-12 space-y-1 text-base">
+      <li>
+        <a
+          href="/a-propos"
+          class="block px-3 py-2 rounded-md text-neutral-800 hover:bg-neutral-100 hover:text-neutral-900 transition-colors"
+        >
+          A propos
+        </a>
+      </li>
+      <li>
+        <a
+          href="/manifeste"
+          class="block px-3 py-2 rounded-md text-neutral-800 hover:bg-neutral-100 hover:text-neutral-900 transition-colors"
+        >
+          Manifeste
+        </a>
+      </li>
+      <li>
+        <a
+          href="/mentions-legales"
+          class="block px-3 py-2 rounded-md text-neutral-800 hover:bg-neutral-100 hover:text-neutral-900 transition-colors"
+        >
+          Mentions legales
+        </a>
+      </li>
+      <!-- TODO V2 : ajouter liens ici (newsletter, soutien Liberapay, contact) -->
+    </ul>
+  </nav>
+</div>
+
+<script>
+  const trigger = document.getElementById('hamburger-trigger');
+  const drawer = document.getElementById('hamburger-drawer');
+  const nav = document.getElementById('hamburger-nav');
+
+  const open = () => {
+    if (!drawer || !nav) return;
+    drawer.classList.remove('hidden');
+    trigger?.setAttribute('aria-expanded', 'true');
+    requestAnimationFrame(() => nav.classList.remove('-translate-x-full'));
+  };
+
+  const close = () => {
+    if (!drawer || !nav) return;
+    nav.classList.add('-translate-x-full');
+    trigger?.setAttribute('aria-expanded', 'false');
+    setTimeout(() => drawer.classList.add('hidden'), 200);
+  };
+
+  trigger?.addEventListener('click', open);
+
+  drawer?.querySelectorAll('[data-drawer-close]').forEach((el) =>
+    el.addEventListener('click', close)
+  );
+
+  // ESC pour fermer
+  document.addEventListener('keydown', (e) => {
+    if (e.key === 'Escape' && drawer && !drawer.classList.contains('hidden')) {
+      close();
+    }
+  });
+</script>