feat: tableur mobile — barres repliées par défaut, bascule unique #189

Sous 768 px, la barre de menus, le ruban et le groupe Recherche sont
repliés par défaut : la barre de formule (fx), les onglets et Enregistrer
restent visibles et la grille récupère la hauteur d'écran. Un bouton
unique (#xlsx-tools-toggle) dans la barre des feuilles déplie/replie
l'ensemble (aria-expanded, état actif) ; desktop inchangé.

Ergonomie tactile : cibles ≥ 44 px, onglets en défilement horizontal,
champs de la barre de formule en 16 px (anti-zoom iOS), barre de formule
en 2 lignes quand les outils sont ouverts.

Tests : JSDOM xlsx-viewer.test.mjs (+2, 165/165), E2E mobile (repli par
défaut, dépliage, no-overflow ruban, cibles 44 px) ; openXlsx() déplie
automatiquement ≤ 768 px pour les tests desktop.

tests/frontend/xlsx-viewer.test.mjs

@@ -2775,6 +2775,54 @@ await test("a read-only workbook keeps the view menus but drops the editing ones
   assert.ok(area.querySelector('[data-xlsx-action="toggle-grid"]'), "Gridlines stay");
 });
 
+// ── #189 — mise en page mobile : barres repliées derrière un basculeur ──────
+
+await test("the sheet strip carries the tools toggle that flips the toolbar (#189)", () => {
+  const area = mountGrid();
+  const strip = area.querySelector(".xlsx-sheetbar");
+  const toggle = area.querySelector("#xlsx-tools-toggle");
+  assert.ok(toggle, "toggle rendered");
+  assert.equal(toggle.closest(".xlsx-sheetbar"), strip, "it lives in the sheet strip");
+  assert.equal(toggle.getAttribute("aria-expanded"), "false", "starts collapsed");
+  const toolbar = area.querySelector(".xlsx-toolbar");
+  assert.ok(!toolbar.classList.contains("xlsx-tools-open"), "toolbar starts closed");
+  toggle.click();
+  assert.ok(toolbar.classList.contains("xlsx-tools-open"), "one click opens the tools");
+  assert.equal(toggle.getAttribute("aria-expanded"), "true");
+  assert.ok(toggle.classList.contains("active"), "the toggle shows its own state");
+  toggle.click();
+  assert.ok(!toolbar.classList.contains("xlsx-tools-open"), "a second click closes them");
+  assert.equal(toggle.getAttribute("aria-expanded"), "false");
+});
+
+await test("style.css hides menus/ribbon/find by default under 768px and reveals them on .xlsx-tools-open (#189)", () => {
+  const css = readFileSync(path.join(REPO_ROOT, "frontend", "style.css"), "utf8");
+  // The desktop default: the toggle itself is out of the way.
+  assert.match(css, /\.xlsx-tools-toggle\s*\{\s*display:\s*none/, "toggle hidden on desktop");
+  // Mobile block: collapsed by default… (CRLF-safe slice, from the #189
+  // comment up to the next top-level rule).
+  const from = css.indexOf("/* #189");
+  assert.ok(from > 0, "the #189 mobile block exists after the coarse-pointer rules");
+  const to = css.indexOf(".xlsx-context-item", from);
+  assert.ok(to > from, "the #189 block is followed by the next rule");
+  const block = css.slice(from, to);
+  for (const cls of [".xlsx-menubar", ".xlsx-cmdbar", ".xlsx-find-group"]) {
+    const hidden = new RegExp(cls.replace(".", "\\.") + "[^}]*display:\\s*none").test(block)
+      || new RegExp(cls.replace(".", "\\.") + ",[\\s\\S]{0,120}?display:\\s*none").test(block);
+    assert.ok(hidden, `${cls} hidden by default on mobile`);
+    assert.ok(
+      block.includes(`.xlsx-toolbar.xlsx-tools-open ${cls}`),
+      `${cls} revealed by .xlsx-tools-open`,
+    );
+  }
+  // The formula bar always stays, and the open state can wrap it (find group).
+  assert.ok(block.includes(".xlsx-toolbar.xlsx-tools-open .xlsx-formula-bar"), "formula bar wraps when open");
+  // Touch: 44px targets, tabs on one scrollable row, 16px inputs (no iOS zoom).
+  assert.match(block, /min-width:\s*44px/, "44px touch targets");
+  assert.match(block, /\.xlsx-sheetbar \.xlsx-tabs\s*\{[^}]*overflow-x:\s*auto/, "tabs scroll horizontally");
+  assert.match(block, /font-size:\s*16px/, "inputs at 16px avoid the iOS focus zoom");
+});
+
 // ── Report ──────────────────────────────────────────────────────────────────
 console.log(`\n${passCount}/${testCount} tests passed\n`);
 process.exit(passCount === testCount ? 0 : 1);