You could probably make a system-level restriction so the software physically can't modify certain files, but I'm not sure how well that's going to fly if the program fails to edit it and there's no feedback of the failure.
With this approach you can enforce that Claude cannot access to specific files. It’s a guarantee and will always work, unlike a prompt or Claude.md which is just a suggestion that can be forgotten or ignored.
This post has an example hook for blocking access to sensitive files:
https://aiorg.dev/blog/claude-code-hooks#:~:text=Protect%20s...