Problem/Motivation
The problem:
The Claro admin theme's layout breaks when you try to add a long string to the CKEditor5 window or try to edit it.
For a more claer desrciption of the issue, see a recording of the bug triggering.
Steps to reproduce
You need a Drupal instance that uses Claro as admin theme. You need a 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.
Expected behaviour:
Width and position of the main content does not change, and the long string does not overflow the CKEditor5 text box.
What happens instead:
As soon as you enter the long string the position of the main content changes, its left/right spacing increases so that the main content region is pushed to the right. If the string is long enough you even have to zoom out in your browser to be able to see the main content.
Proposed resolution
Add theming changes to Claro.