fix: double TOC in published view and broken collapsible sections

- Add missing mobile TOC styles (display:none defaults, sidebar panel,
backdrop, toggle button) extracted from TableOfContents.astro
- Add overflow:hidden + transition for toc-collapsible sub-sections

Made-with: Cursor

frontend/src/styles/components/_toc.css

@@ -4,6 +4,18 @@
 /* Shared between editor and publisher.                                        */
 /* ============================================================================ */
 
+/* Loading state */
+.table-of-contents.toc-loading,
+.toc-mobile-sidebar.toc-loading {
+  opacity: 0;
+  transition: opacity 0.3s ease-in-out;
+}
+.table-of-contents.toc-loaded,
+.toc-mobile-sidebar.toc-loaded {
+  opacity: 1;
+}
+
+/* Desktop TOC */
 .table-of-contents {
   position: sticky;
   top: 32px;
@@ -53,3 +65,159 @@
 .table-of-contents nav a.active {
   text-decoration: underline;
 }
+
+/* Collapsible sub-sections (JS adds class toc-collapsible and inline height) */
+.toc-collapsible li > ul {
+  overflow: hidden;
+  transition: height 200ms ease;
+}
+.toc-collapsible li.collapsed > ul {
+  display: block;
+}
+
+/* ============================================================================ */
+/* Mobile TOC - toggle button                                                   */
+/* Hidden on desktop, shown via _layout.css @media (--bp-content-collapse)      */
+/* ============================================================================ */
+
+.toc-mobile-toggle {
+  display: none;
+  position: fixed;
+  top: var(--spacing-4);
+  right: var(--spacing-4);
+  z-index: var(--z-overlay);
+  width: 40px;
+  height: 40px;
+  border-radius: 50%;
+  border: 1px solid var(--border-color);
+  background: var(--page-bg);
+  box-shadow: 0 2px 12px rgba(0,0,0,.08);
+  align-items: center;
+  justify-content: center;
+  padding: 0;
+  cursor: pointer;
+  color: var(--text-color);
+  transition: transform 150ms ease, box-shadow 150ms ease;
+}
+.toc-mobile-toggle:active {
+  transform: scale(0.92);
+}
+
+/* ============================================================================ */
+/* Mobile TOC - backdrop                                                        */
+/* ============================================================================ */
+
+.toc-mobile-backdrop {
+  display: none;
+  position: fixed;
+  inset: 0;
+  z-index: var(--z-overlay);
+  background: rgba(0,0,0,.4);
+  opacity: 0;
+  pointer-events: none;
+  transition: opacity 250ms ease;
+}
+.toc-mobile-backdrop.open {
+  opacity: 1;
+  pointer-events: auto;
+}
+
+/* ============================================================================ */
+/* Mobile TOC - sidebar panel                                                   */
+/* ============================================================================ */
+
+.toc-mobile-sidebar {
+  display: none;
+  position: fixed;
+  top: 0;
+  right: 0;
+  bottom: 0;
+  z-index: calc(var(--z-overlay) + 1);
+  width: min(320px, 85vw);
+  background: var(--page-bg);
+  border-left: 1px solid var(--border-color);
+  transform: translateX(100%);
+  transition: transform 300ms cubic-bezier(.4,0,.2,1);
+  flex-direction: column;
+}
+.toc-mobile-sidebar.open {
+  transform: translateX(0);
+}
+
+.toc-mobile-sidebar__header {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  padding: 16px;
+  border-bottom: 1px solid var(--border-color);
+  flex-shrink: 0;
+}
+
+.toc-mobile-sidebar__title {
+  font-weight: 700;
+  font-size: 15px;
+  color: var(--text-color);
+}
+
+.toc-mobile-sidebar__actions {
+  display: flex;
+  align-items: center;
+  gap: 4px;
+}
+
+.toc-mobile-sidebar__close,
+.toc-mobile-sidebar__theme {
+  background: none;
+  border: none;
+  color: var(--muted-color);
+  cursor: pointer;
+  padding: 4px;
+  border-radius: 6px;
+  width: 32px;
+  height: 32px;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  transition: color 150ms ease, background 150ms ease;
+}
+.toc-mobile-sidebar__close:hover,
+.toc-mobile-sidebar__theme:hover {
+  color: var(--text-color);
+  background: var(--surface-bg);
+}
+
+.toc-mobile-sidebar__body {
+  flex: 1;
+  overflow-y: auto;
+  -webkit-overflow-scrolling: touch;
+  padding: 16px;
+}
+
+/* TOC styles inside mobile sidebar */
+.toc-mobile-sidebar nav ul {
+  margin: 0 0 6px;
+  padding-left: 1em;
+}
+.toc-mobile-sidebar nav li {
+  list-style: none;
+  margin: 0.35em 0;
+}
+.toc-mobile-sidebar nav a,
+.toc-mobile-sidebar nav a:link,
+.toc-mobile-sidebar nav a:visited {
+  color: var(--text-color);
+  text-decoration: none;
+  border-bottom: none;
+  font-size: 14px;
+  line-height: 1.5;
+}
+.toc-mobile-sidebar nav > ul > li > a {
+  font-weight: 700;
+}
+.toc-mobile-sidebar nav a:hover {
+  text-decoration: underline solid var(--muted-color);
+}
+.toc-mobile-sidebar nav a.active {
+  color: var(--primary-color);
+  text-decoration: underline;
+}