sensible LLMs docs instead of "copy for LLM"

Adopt Anhtopics documentation style where any web page has .md appended to it and can be given to LLM for consumption

example: landing page
https://code.claude.com/docs/en/overview
https://code.claude.com/docs/en/overview.md

crucially has an index https://code.claude.com/docs/llms.txt