Redesign: Fix feature flag attribute not being applied when only server-side flag is enabled (#40547)

app/javascript/inline/theme-selection.js

@@ -21,13 +21,4 @@
 
   updateColorScheme();
   updateContrast();
-
-  const isRedesignEnabled = (
-    window.localStorage.getItem('experiments')?.split(',') ?? []
-  ).includes('redesign');
-
-  if (isRedesignEnabled) {
-    element.dataset.redesign = true;
-  }
-
 })(document.documentElement);

app/javascript/mastodon/main.tsx

@@ -10,7 +10,11 @@ import { me, reduceMotion } from 'mastodon/initial_state';
 import ready from 'mastodon/ready';
 import { store } from 'mastodon/store';
 
-import { isDevelopment, isProduction } from './utils/environment';
+import {
+  isDevelopment,
+  isProduction,
+  isRedesignEnabled,
+} from './utils/environment';
 
 function main() {
   perf.start('main()');
@@ -33,6 +37,10 @@ function main() {
     const { initializeEmoji } = await import('./features/emoji/index');
     await initializeEmoji();
 
+    if (isRedesignEnabled()) {
+      document.documentElement.dataset.redesign = 'true';
+    }
+
     const root = createRoot(mountNode);
     root.render(
       <StrictMode>