One llms.txt for every Core API page

AI assistants and coding agents can now find every Core API page from a single file. llms.txt lists all 94 V3 and V1 pages, with links to their Markdown versions.

What's in it:

• Key facts first: base URLs, authentication, pagination, errors and rate limits.
• Every endpoint entry starts with its HTTP method and full URL.
• The V1 reference is included. The previous file left it out entirely.