Align "home-page info" file priority in build_llm_docs to that of actual home-page generation (pkgdown/index.md > index.md > README.md)

[koefoeden]

EDIT: See comment below.
Original message: Currently, build_llm_docs just uses the content in README.md for the high-level overview of the package in LLMs.txt. However, this is inconsistent with the actual homepage, which uses the more sophisicated file prioritization, as seen here: https://pkgdown.r-lib.org/reference/build_home.html#home-page.

[koefoeden]

Ah, turns out it actually works for example by having your home-page info in pkgdown/index.md, because this is turned into index.html during build_home(), which is then backconverted into index.md by convert_md in build_llm_docs. But in genereal, it looks like build_llm_docs effectively overwrites your previous .md templates with the back-converted variants - could this be problematic? Perhaps a better (and faster way) is just to use the .md files if they exist?

[koefoeden]

In any way, the docs on build_llm_docs() should perhaps be updated to reflect this - i.e. that it's actually based on your index.html, and not README.md