LLVM-based API checker

[nlohmann]

It would be great to use LLVM/Clang to traverse the AST of the library and collect all public types and functions to programmatically derive "the public API". Once we have that, we can do the following to improve the project:

• Check if every public API function has a link to a documentation page.
• Check how the list of public API functions changes for a new release.
  • New functions would usually mean a feature release.
  • Changed or deleted functions would usually mean a breaking change.

Looking at the examples out there (e.g., https://github.com/banach-space/clang-tutor), this should be pretty straightforward. I would not go so far and claim we can make any proof about API stability, but I think such a tool would in any case help to be more conscious about the API and its documentation.

[nlohmann]

Looking into it.

---

This reply was drafted by Claude Code on behalf of @nlohmann, as part of a review of open discussions.