Fix missing .rsc outputs for pages prerenders (#11503)

When generating the outputs for pages when app router is also present we weren't creating the placeholder `.rsc` outputs for all prerender outputs so when a `fallback: false` route was configured in the pages router that could fall through to an app route it causes issues with client-navigation behaving differently than a direct visit. 

This ensures we add the placeholder `.rsc` outputs for all prerenders so that `fallback: false` pages don't have this unexpected behavior.

packages/next/src/utils.ts

@@ -2477,6 +2477,22 @@ export const onPrerenderRoute =
         });
       }
 
+      // we need to ensure all prerenders have a matching .rsc output
+      // otherwise routing could fall through unexpectedly for the
+      // fallback: false case as it doesn't have a dynamic route
+      // to catch the `.rsc` request for app -> pages routing
+      if (outputPrerenderPathData?.endsWith('.json') && appDir) {
+        const dummyOutput = new FileBlob({
+          data: '{}',
+          contentType: 'application/json',
+        });
+        const rscKey = `${outputPathPage}.rsc`;
+        const prefetchRscKey = `${outputPathPage}${RSC_PREFETCH_SUFFIX}`;
+
+        prerenders[rscKey] = dummyOutput;
+        prerenders[prefetchRscKey] = dummyOutput;
+      }
+
       ++prerenderGroup;
 
       if (routesManifest?.i18n && isBlocking) {