An index of the site, in Markdown, at the path the llmstxt.org convention names.

## Response

`text/plain`. The site title and description, then every page as a linked list
item to its `.md` representation with its own description.

## Notes

Generated for every served locale from each source's default version only. A
model handed every version of every page has to work out which one is current,
and the answer to that question is a build-time fact the site already knows.