test(e2e): Trigger INP flush via visibilitychange instead of pagehide

The Safari 14 support removal dropped the `pagehide` listener from the
vendored web-vitals code, so the React/react-router SPA E2E apps that
flushed the INP span by dispatching a bare `pagehide` event no longer
triggered a flush and timed out. Switch them to the same
`visibilitychange` pattern already used in the browser integration tests.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: msonnb

dev-packages/e2e-tests/test-applications/react-17/tests/transactions.test.ts

@@ -80,7 +80,8 @@ test('sends an INP span', async ({ page }) => {
 
   // Page hide to trigger INP
   await page.evaluate(() => {
-    window.dispatchEvent(new Event('pagehide'));
+    Object.defineProperty(document, 'visibilityState', { value: 'hidden', configurable: true });
+    document.dispatchEvent(new Event('visibilitychange'));
   });
 
   const inpSpan = await inpSpanPromise;

dev-packages/e2e-tests/test-applications/react-router-6/tests/transactions.test.ts

@@ -80,7 +80,8 @@ test('sends an INP span', async ({ page }) => {
 
   // Page hide to trigger INP
   await page.evaluate(() => {
-    window.dispatchEvent(new Event('pagehide'));
+    Object.defineProperty(document, 'visibilityState', { value: 'hidden', configurable: true });
+    document.dispatchEvent(new Event('visibilitychange'));
   });
 
   const inpSpan = await inpSpanPromise;

dev-packages/e2e-tests/test-applications/react-router-7-spa-streaming/tests/spans.test.ts

@@ -60,7 +60,8 @@ test('sends an INP span', async ({ page }) => {
 
   // Page hide to trigger INP
   await page.evaluate(() => {
-    window.dispatchEvent(new Event('pagehide'));
+    Object.defineProperty(document, 'visibilityState', { value: 'hidden', configurable: true });
+    document.dispatchEvent(new Event('visibilitychange'));
   });
 
   const inpSpan = await inpSpanPromise;

dev-packages/e2e-tests/test-applications/react-router-7-spa/tests/transactions.test.ts

@@ -80,7 +80,8 @@ test('sends an INP span', async ({ page }) => {
 
   // Page hide to trigger INP
   await page.evaluate(() => {
-    window.dispatchEvent(new Event('pagehide'));
+    Object.defineProperty(document, 'visibilityState', { value: 'hidden', configurable: true });
+    document.dispatchEvent(new Event('visibilitychange'));
   });
 
   const inpSpan = await inpSpanPromise;

dev-packages/e2e-tests/test-applications/react-router-8-spa/tests/transactions.test.ts

@@ -80,7 +80,8 @@ test('sends an INP span', async ({ page }) => {
 
   // Page hide to trigger INP
   await page.evaluate(() => {
-    window.dispatchEvent(new Event('pagehide'));
+    Object.defineProperty(document, 'visibilityState', { value: 'hidden', configurable: true });
+    document.dispatchEvent(new Event('visibilitychange'));
   });
 
   const inpSpan = await inpSpanPromise;