fix(sandpack): make Clear button actually reset the preview

When the Clear button reset edited files, it also called refresh()
synchronously. The refresh reboots the preview iframe while the
Sandpack client still holds the edited files, and the debounced file
sync carrying the reset files is lost in the reboot. The preview then
keeps running the edited code.

Only refresh when there was nothing to reset; after a confirmed reset,
let the file watcher push the original files so the bundler recompiles
the preview with them.

Fixes #8657

Author: Dextheking1

src/components/MDX/Sandpack/NavigationBar.tsx

@@ -110,15 +110,15 @@ export function NavigationBar({
   }, [isMultiFile, onContainerResize]);
 
   const handleClear = () => {
-    /**
-     * resetAllFiles must come first, otherwise
-     * the previous content will appear for a second
-     * when the iframe loads.
-     *
-     * Plus, it should only prompt if there's any file changes
-     */
+    // Only prompt when there are edits to clear.
     if (sandpack.editorState === 'dirty' && confirm('Clear all your edits?')) {
       sandpack.resetAllFiles();
+      // Don't refresh() here. The reset files are pushed to the bundler by
+      // the file watcher, which recompiles the preview with the original
+      // code. Refreshing synchronously would reboot the iframe while the
+      // client still holds the edited files: the reset compile is lost in
+      // the reboot, so the preview keeps running the edited code (#8657).
+      return;
     }
     refresh();
   };