LLM chat should support diagrams with mermaid

We should enable our agent to provide a mermaid diagram to the user. These can be helpful to display how resources are depending on each other.

Here is a case where it didn't work:

<img width="789" height="1016" alt="Image" src="https://github.com/user-attachments/assets/5ec9afa6-87bf-4b31-9458-f34d318f5f31" />