// Title search and tab-state handling land in Task 7.
function setActiveTab(el) {
  el.parentElement.querySelectorAll("[role=tab]").forEach(function (t) {
    t.classList.toggle("active", t === el);
  });
}

function toggleChapterForm(key) {
  var form = document.getElementById("chapter-form-" + key);
  if (!form) return;
  form.hidden = !form.hidden;
  if (!form.hidden) form.querySelector("input").focus();
}