Trigger error for stream on client when it is not finished as expected (

#65798)

### What

* Error on case that readable stream controller tries to close but
stream is either errored or unfinished
* Delay the DOMContentLoaded event to avoid "Connection Closed" error


### Why

Regarding to the new error about readbale stream controller, the new
error we added here is for identifying the connection is closing before
the last bit has been received that's an error case not intentional
close. It's not a proper state for close more for erroring.


As for adding the queuing for the task of dom content loaded callback,
after investigation, I found that if the DOMLoaded execute earlier the
readable stream controller cuold close earlier on client, which lead to
the "Connection Closed." error. Hence we added a `queueMicroTask` here
to delay it after hydrate call.

x-ref: [slack
thread](https://vercel.slack.com/archives/C01A2M9R8RZ/p1715188343813489)

packages/next/src/client/app-index.tsx

@@ -73,6 +73,11 @@ function nextServerDataCallback(
   }
 }
 
+function isStreamErrorOrUnfinished(ctr: ReadableStreamDefaultController) {
+  // If `desiredSize` is null, it means the stream is closed or errored. If it is lower than 0, the stream is still unfinished.
+  return ctr.desiredSize === null || ctr.desiredSize < 0
+}
+
 // There might be race conditions between `nextServerDataRegisterWriter` and
 // `DOMContentLoaded`. The former will be called when React starts to hydrate
 // the root, the latter will be called when the DOM is fully loaded.
@@ -87,7 +92,15 @@ function nextServerDataRegisterWriter(ctr: ReadableStreamDefaultController) {
       ctr.enqueue(encoder.encode(val))
     })
     if (initialServerDataLoaded && !initialServerDataFlushed) {
-      ctr.close()
+      if (isStreamErrorOrUnfinished(ctr)) {
+        ctr.error(
+          new Error(
+            'The connection to the page was unexpectedly closed, possibly due to the stop button being clicked, loss of Wi-Fi, or an unstable internet connection.'
+          )
+        )
+      } else {
+        ctr.close()
+      }
       initialServerDataFlushed = true
       initialServerDataBuffer = undefined
     }
@@ -105,11 +118,13 @@ const DOMContentLoaded = function () {
   }
   initialServerDataLoaded = true
 }
+
 // It's possible that the DOM is already loaded.
 if (document.readyState === 'loading') {
   document.addEventListener('DOMContentLoaded', DOMContentLoaded, false)
 } else {
-  DOMContentLoaded()
+  // Delayed in marco task to ensure it's executed later than hydration
+  setTimeout(DOMContentLoaded)
 }
 
 const nextServerDataLoadingGlobal = ((self as any).__next_f =