[facebook/react] Bug: startTransition inside popstate shows Suspense fallback instead of previous UI

### ROOT CAUSE The issue occurs because `startTransition` marks the `popstate` event handler as a new React transition, causing the Suspense fallback to be shown during the navigation. This happens because `popstate` events should not trigger new transitions since they restore the previous state. React's `startTransition` optimizes rendering for new content but conflicts with the purpose of `popstate`, which is to retrieve existing data without prioritizing new rendering. ### CODE FIX Remove `startTransition` from the `popstate` event handler to prevent it from being treated as a new React transition. Instead, handle state updates directly. ```javascript // Before (problematic) window.addEventListener('popstate', () => { startTransition(() => { // Update state to load previous data }); }); // After (fixed) window.addEventListener('popstate', () => { // Update state to load previous data directly }); ```