Add global nav dropdown behavior

static/js/core/global-nav.js

@@ -0,0 +1,48 @@
+(() => {
+    const dropdowns = Array.from(document.querySelectorAll('.mode-nav-dropdown'));
+    if (!dropdowns.length) return;
+
+    const closeAll = () => {
+        dropdowns.forEach((dropdown) => dropdown.classList.remove('open'));
+    };
+
+    const openDropdown = (dropdown) => {
+        if (!dropdown.classList.contains('open')) {
+            closeAll();
+            dropdown.classList.add('open');
+        }
+    };
+
+    document.addEventListener('click', (event) => {
+        const menuLink = event.target.closest('.mode-nav-dropdown-menu a');
+        if (menuLink) {
+            event.preventDefault();
+            event.stopPropagation();
+            window.location.href = menuLink.href;
+            return;
+        }
+
+        const button = event.target.closest('.mode-nav-dropdown-btn');
+        if (button) {
+            event.preventDefault();
+            const dropdown = button.closest('.mode-nav-dropdown');
+            if (!dropdown) return;
+            if (dropdown.classList.contains('open')) {
+                dropdown.classList.remove('open');
+            } else {
+                openDropdown(dropdown);
+            }
+            return;
+        }
+
+        if (!event.target.closest('.mode-nav-dropdown')) {
+            closeAll();
+        }
+    });
+
+    document.addEventListener('keydown', (event) => {
+        if (event.key === 'Escape') {
+            closeAll();
+        }
+    });
+})();