Nice work. I made a similar (but much less capable) Python script [1] for my own use before and I can say that a tool like this is useful to keep the docs in sync with the code.

My script only detects whether a checksum for a segment of code doesn't match, using directives placed in the code (not a separate file as you've done). For example:

    #tripwire$ begin 094359D3 Update docs section blah if necessary.
    [...]
    #tripwire$ end

Also, my script knows nothing about pull requests and is basically a linter. So it's definitely not as capable.

[1] https://github.com/btrettel/flt/blob/main/py/tripwire.py

***

Edit: I just checked my notes. I might have got the idea for my script from this earlier Hacker News comment: https://news.ycombinator.com/item?id=25423514