Restore GA page_view parity with the Pages Router

`send_page_view: false` suppressed GA4's automatic page_view on landing,
and the custom `pageview` event was sent for every pathname including the
initial one. Match the old _app.tsx: let gtag('config') report the landing
page_view, and only send the legacy custom event on client navigations.

Co-Authored-By: Claude <noreply@anthropic.com>

Author: gaearon

src/app/clientEffects.tsx

@@ -7,16 +7,22 @@
 
 'use client';
 
-import {useEffect} from 'react';
+import {useEffect, useRef} from 'react';
 import {usePathname} from 'next/navigation';
 
 declare const gtag: (...args: any[]) => void;
 
 export function AnalyticsTracker() {
   const pathname = usePathname();
+  const previousPathname = useRef(pathname);
 
   useEffect(() => {
-    if (typeof window === 'undefined' || typeof gtag === 'undefined') return;
+    // The initial page view is reported by gtag('config') itself. This
+    // mirrors the Pages Router's `routeChangeComplete` handler, which only
+    // fired for client-side navigations.
+    if (previousPathname.current === pathname) return;
+    previousPathname.current = pathname;
+    if (typeof gtag === 'undefined') return;
     gtag('event', 'pageview', {event_label: pathname});
   }, [pathname]);
 

src/app/layout.tsx

@@ -209,7 +209,7 @@ export default function RootLayout({children}: {children: React.ReactNode}) {
             id="ga-init"
             strategy="afterInteractive"
             dangerouslySetInnerHTML={{
-              __html: `window.dataLayer = window.dataLayer || [];function gtag(){dataLayer.push(arguments);}gtag('js', new Date());gtag('config', '${gaId}', {send_page_view: false});`,
+              __html: `window.dataLayer = window.dataLayer || [];function gtag(){dataLayer.push(arguments);}gtag('js', new Date());gtag('config', '${gaId}');`,
             }}
           />
         )}