Most of the architecture diagrams that I review and sometimes write are of the second kind. Once you have planned and set for execution, the architecture rarely changes. If it did, then there was something fundamentally wrong with the first architecture and as s result this diagram will be modified in a review or a rewrite or whatever.

A live architecture document derived from code, even on a batch basis if not in real time, will be a really cool endeavour. If you can somehow look at a repo and generate a diagram describing all the different subsystems and their interactions, boy imagine that !

A simple traceability might be just through imports starting with the main program. Start with the main functions and trace them through. May be using a tool like sourcegraph.