Initialize compact mode on MozBeforeInitialXULLayout event

src/browser/base/content/ZenStartup.mjs

@@ -30,7 +30,6 @@
 
         this._initSidebarScrolling();
 
-        gZenCompactModeManager.preInit();
         ZenWorkspaces.init();
         gZenVerticalTabsManager.init();
         gZenUIManager.init();

src/browser/base/zen-components/ZenCompactMode.mjs

@@ -508,3 +508,11 @@ var gZenCompactModeManager = {
     }
   },
 };
+
+document.addEventListener(
+  'MozBeforeInitialXULLayout',
+  () => {
+    gZenCompactModeManager.preInit();
+  },
+  { once: true }
+);