Looks good overall.

The only concern I've had for a long time is that the main.md (now index.md) is (mostly) a duplication of the main README for the project. Any chance there's a way to avoid this duplication? Probably outside the immediate scope of this PR, but something to think about.

100% a fair concern!

I've personally wanted to mostly strip out the readmes, and replace with this

• Top level readme.md is short overview linking to docs
• Subproject README.md files are basically for developer contributing guides - "I've checked out the project and open the readme file in my IDE, it should probably tell me to uv sync next or whatever" - like stuff that only makes sense when you have it checked out. Everything else in some other docs files

This might cause some duplication though so potentially throw it all in docs/ and only link.