Add options & state around expand/collapse

js/archive_tree.js

@@ -0,0 +1,22 @@
+(function () {
+  // Wait for DOM ready
+  document.addEventListener('DOMContentLoaded', function () {
+    document.querySelectorAll('.archive-tree-year').forEach(function (summary) {
+      var details = summary.parentElement;
+      var year = summary.querySelector('a')?.textContent?.trim();
+      if (!year) return;
+      var key = 'archive_tree_year_' + year;
+      // Restore state
+      var open = localStorage.getItem(key);
+      if (open === 'true') {
+        details.setAttribute('open', '');
+      } else if (open === 'false') {
+        details.removeAttribute('open');
+      }
+      // Listen for toggle
+      details.addEventListener('toggle', function () {
+        localStorage.setItem(key, details.open ? 'true' : 'false');
+      });
+    });
+  });
+})();