fix(app): timeline width jumps around when review panel is open/closed (#36202)

packages/app/src/pages/session.tsx

@@ -483,7 +483,7 @@ export default function Page() {
     if (desktopSessionResizeOpen()) return `${sessionPanelResizedWidth()}px`
     return `calc(100% - ${layout.fileTree.width()}px)`
   })
-  const centered = createMemo(() => isDesktop() && !desktopReviewOpen())
+  const centered = createMemo(() => isDesktop() && (newSessionDesign() || !desktopReviewOpen()))
   const desktopV2PanelLayout = createMemo(() =>
     sessionPanelLayout({
       review: desktopV2ReviewOpen(),