No llms.txt file generated

In https://github.com/panel-extensions/panel-material-ui/pull/366 I'm adding `sphinx-llm` to `panel-material-ui` docs.

But I experience the `llms.txt` file is not created.

<img width="332" height="210" alt="Image" src="https://github.com/user-attachments/assets/3462f024-c948-4024-887a-0b5bdb21b6d5" />

Please help or fix. Thanks.