llmstxt.org should have an llms.txt

I'd like to tell my agent to use llmstxt.org to generate an llms.txt file for a given repository if it doesn't have one already

Start by reviewing the issue request and llmstxt.org to understand the expected generation flow for a repository without an llms.txt file. No implementation file or test is named, so identify the relevant entry point and define done as producing the requested file when it is absent.

Written by the indexing model from the issue text.