feat(ui): add flicker detection and metrics (#10821)

packages/cli/src/ui/AppContainer.tsx

@@ -210,6 +210,8 @@ export const AppContainer = (props: AppContainerProps) => {
 
   // Layout measurements
   const mainControlsRef = useRef<DOMElement>(null);
+  // For performance profiling only
+  const rootUiRef = useRef<DOMElement>(null);
   const originalTitleRef = useRef(
     computeWindowTitle(basename(config.getTargetDir())),
   );
@@ -1148,6 +1150,7 @@ Logging in with Google... Please restart Gemini CLI to continue.
       terminalWidth,
       terminalHeight,
       mainControlsRef,
+      rootUiRef,
       currentIDE,
       updateInfo,
       showIdeRestartPrompt,
@@ -1227,6 +1230,7 @@ Logging in with Google... Please restart Gemini CLI to continue.
       terminalWidth,
       terminalHeight,
       mainControlsRef,
+      rootUiRef,
       currentIDE,
       updateInfo,
       showIdeRestartPrompt,