Mermaid: hit the "expand" button (far right) and the diagram was cut off

Testing #316726

<img width="456" height="585" alt="Image" src="https://github.com/user-attachments/assets/8113a326-d93c-44c1-9a83-1b9021016ebf" />

Steps:
* have a few different charts up
* hit the button on the right
* 🐛 the graph is cut off