Add product category tree sidebar to archive and single product pages (v0.1.7)

Hierarchical category navigation with collapsible sub-levels up to 3 levels
deep, using Bootstrap 5 list-group and collapse components. Sidebar renders
on both archive/shop and single product pages with responsive offcanvas on
mobile. Active category highlighting and ancestor auto-expand for intuitive
navigation.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

assets/css/wc-bootstrap.css

@@ -644,3 +644,50 @@ header.sticky-top.is-stuck {
 .woocommerce-product-gallery--without-images {
     opacity: 1 !important;
 }
+
+/* ==========================================================================
+   Category Tree Sidebar
+   Hierarchical product category navigation with collapsible sub-levels.
+   ========================================================================== */
+
+.category-tree {
+    font-size: 0.9rem;
+}
+
+.category-tree .list-group-item {
+    background-color: transparent;
+}
+
+.category-tree-link {
+    color: var(--bs-body-color);
+    transition: background-color 0.15s ease, color 0.15s ease;
+}
+
+.category-tree-link:hover {
+    background-color: var(--bs-tertiary-bg);
+    color: var(--bs-body-color);
+}
+
+.category-tree-link.active {
+    background-color: var(--bs-primary);
+    color: #fff;
+}
+
+.category-tree-link.active .badge {
+    background-color: rgba(255, 255, 255, 0.2) !important;
+    color: #fff !important;
+}
+
+/* Rotate chevron icon when collapsed/expanded */
+.category-tree-toggle .bi {
+    transition: transform 0.2s ease;
+}
+
+.category-tree-toggle[aria-expanded="false"] .bi {
+    transform: rotate(-90deg);
+}
+
+/* Nested list indentation */
+.category-tree .list-group-flush .list-group-flush {
+    padding-left: 0.75rem;
+}