feat: onglet de navigation avec facettes, tris et retour Home complet #158

- clic sur un repertoire de l'arbre (modes focus vault et All) ouvre un onglet de navigation dedie qui coexiste avec les onglets de fichiers ouverts
- vue: sous-repertoires cliquables, facettes Vaults/Tags/Extensions (meme mecanisme que la recherche), tris Pertinence/Date, bouton Sauver; tags indexes exposes par GET /api/vault/{v}/files
- BUG-100: showWelcome re-injecte la section Raccourcis & Astuces et goHome efface la recherche globale + le filtre de la sidebar

frontend/js/viewer.js

@@ -4120,9 +4120,23 @@ export function highlightSearchText(container, text, query, caseSensitive) {
   }
 }
 
+// #158 — the static « Raccourcis & Astuces » block lives in index.html inside
+// #dashboard-panel-stats; showWelcome() rebuilds #dashboard-home from a
+// template that omits it, so the block disappeared after the first rebuild.
+// Capture it once, at module load (before any rebuild can destroy it).
+const QUICK_HELP_HTML = (() => {
+  if (typeof document === "undefined") return "";
+  const qh = document.getElementById("quick-help");
+  return qh ? qh.outerHTML : "";
+})();
+
 export function showWelcome() {
   hideProgressBar();
 
+  // #158 — the dashboard takes over the content area: drop the active-tab
+  // marker so clicking a tab re-renders it instead of early-returning.
+  if (window.TabManager && window.TabManager.deactivate) window.TabManager.deactivate();
+
   // Restore or rebuild the dashboard with tabbed sections
   const area = getContentArea();
   // #110 — keep playing media alive if the dashboard replaces its surface.
@@ -4154,6 +4168,7 @@ export function showWelcome() {
             <div class="dashboard-stats-loading" data-i18n="common.loading">${t('common.loading')}</div>
           </div>
           <div id="dashboard-conflicts-container" style="margin-top:16px"></div>
+          ${QUICK_HELP_HTML}
         </div>
 
         <!-- Bookmarks Panel -->