docs: Use expandable code block instead of accordion for full example

Author: beran-t

docs/examples/app-preview.mdx

@@ -112,8 +112,7 @@ for entry in report:
 
 ## Full example
 
-<Accordion title="View full code">
-```python app_preview.py
+```python app_preview.py expandable
 """
 App Preview — E2B + Kernel
 
@@ -251,7 +250,6 @@ def main():
 if __name__ == "__main__":
     main()
 ```
-</Accordion>
 
 ## Key concepts