a11y job fails looking for `proof-a11y.json`

**Describe the bug**

In a new design system, the `a11y` CI job fails with `Error: ENOENT: no such file or directory, open 'proof-a11y.json'.

**To Reproduce**

1. Follow the Getting Started instructions to generate and set up a new design system.
2. Run CI.

**Expected behavior**

Something would tell me what `proof-a11y.json` and how to create it (or create it for me).

I assume this is just something missing in the docs?