fix: Trigger window._sp_.executeMessaging() after the pageshow event (#2196)

* Add event listener for pageshow

* Add changeset

* Check if event is persisted before triggering.

Author: akinsola-guardian

.changeset/curvy-seas-brush.md

@@ -0,0 +1,5 @@
+---
+'@guardian/libs': minor
+---
+
+Add pageshow event listener for pageshow event to ensure the Consent or Pay banner is shown after clicking the Browser's back button

libs/@guardian/libs/src/consent-management-platform/sourcepoint.ts

@@ -362,6 +362,14 @@ export const init = (
 		}
 	});
 
+	// Handle back navigation to ensure CMP messaging is shown when needed
+	window.addEventListener('pageshow', (event: PageTransitionEvent) => {
+		// Only re-execute messaging if the page is being loaded from cache i.e. via back/forward navigation
+		if (event.persisted) {
+			window._sp_?.executeMessaging?.();
+		}
+	});
+
 	spLib.src = `${ENDPOINT}/unified/wrapperMessagingWithoutDetection.js`;
 
 	document.body.appendChild(spLib);