Improve debug panel toggle with proper state tracking

index.html

@@ -49,6 +49,9 @@
             color: var(--icon);
             margin-left: 8px;
         }
+        .debug-content.collapsed {
+            display: none;
+        }
         .debug-section {
             font-size: 1em;
             color: var(--icon);
@@ -1136,12 +1139,13 @@ var weatherThemes = {
             var content = document.getElementById('debug-content');
             var title = document.querySelector('.debug-title');
             var icon = document.getElementById('debug-toggle-icon');
-            if (content.style.display === 'none') {
-                content.style.display = '';
+            var isCollapsed = content.classList.contains('collapsed');
+            if (isCollapsed) {
+                content.classList.remove('collapsed');
                 title.classList.add('expanded');
                 icon.textContent = '▼';
             } else {
-                content.style.display = 'none';
+                content.classList.add('collapsed');
                 title.classList.remove('expanded');
                 icon.textContent = '▶';
             }