menu: restore reliable polling (setInterval 500ms) so the item always appears even if plugin loads before menu

plugin.js

@@ -418,6 +418,8 @@
         $('.menu .menu__list').eq(0).append(makeButton());
         if (Lampa.Selector) Lampa.Selector.update();
     }
+    var menuSubscribed = false;
+    var menuInterval = null;
     function start() {
         if (menuSubscribed) return;
         menuSubscribed = true;
@@ -425,6 +427,15 @@
         // Register localized strings for this plugin.
         try { Lampa.Lang.add(STRINGS); } catch (e) { /* older Lampa: ignore */ }
 
+        function tryAdd() {
+            if ($('.menu .menu__list').length && !$('[data-action="' + PLUGIN.menu_action + '"]').length) {
+                addMenuButton();
+                if (menuInterval) { clearInterval(menuInterval); menuInterval = null; }
+                return true;
+            }
+            return false;
+        }
+
         Lampa.Listener.follow('menu', function (e) {
             if (e.type === 'start' && e.body) {
                 var list = e.body.find('.menu__list');
@@ -432,13 +443,17 @@
                 // guard against duplicate copies in this menu body
                 if (list.find('[data-action="' + PLUGIN.menu_action + '"]').length) return;
                 addMenuButton();
+                if (menuInterval) { clearInterval(menuInterval); menuInterval = null; }
             }
         });
 
-        // If the main menu is already built, add the item immediately so it does
-        // NOT appear late and shove other items around.
-        if ($('.menu .menu__list').length && !$('[data-action="' + PLUGIN.menu_action + '"]').length) {
-            addMenuButton();
+        // The main menu may already be built (or built later) by the time this plugin
+        // loads. Poll briefly (every 500ms) until it appears, then add the item once.
+        // This keeps it from showing "late and shoving items" while still being reliable.
+        if (!tryAdd()) {
+            menuInterval = setInterval(tryAdd, 500);
+            // safety: stop polling after 30s regardless
+            setTimeout(function () { if (menuInterval) { clearInterval(menuInterval); menuInterval = null; } }, 30000);
         }
     }