Long string breaks the layout

Problem/Motivation

The problem:
The Claro admin theme's layout breaks when you try to add a long string to the CKEditor5 window.

Steps to reproduce

You need a Drupal instance with a Basic page content type that has a body field which uses a text format that uses CKEditor5.
Try to create a new node and add a long string, which is at least 200 characters long to be sure to see the issue.
You will experience that the distance/gap between the main region and secondary region becomes huge, you probably need to zoom out to find anything but the white background.

Proposed resolution

Add theming changes to Claro.

Remaining tasks

User interface changes

API changes

Data model changes