I am sure that this exists for other ecosystems as well - rustdoc, Documenter.jl and Sphinx seem to support this - but my experience lies in R: three of the Diátaxis categories map quite nicely onto R package constructs:

- Tutorials are implemented as "vignettes", executed on package validation - How-Tos are attached in roxygen documentation chunks, likewise executable by default - execution disabled when expensive or to avoid side effects. - Reference is implemented in a TeX or Markdown format, commonly parsed by roxygen

The only thing that's missing is a canonical way of documenting implementation rationale. Having the documentation outside the repo worked before LLMs, but there was always that weak point of code drifting away from the documentation...

Something that Python gets right is that their entire docs site is versioned - select 2.7.18, for example, and you get the 2.7 docs right down to the tutorial. The Python development process is also very careful about keeping documentation up to date; the PEP process even requires an explicit "How to Teach This" section for proposals that add or change language features.