Add AI readiness files (CLAUDE.md, llms.txt, .cursorrules, Copilot instructions)

[MariJJhodl]

What this PR adds

Four files to help AI assistants work correctly with this documentation repo:

File	Tool
CLAUDE.md	Claude Code (Anthropic)
llms.txt	Open standard — read by various LLM tools and AI crawlers
.cursorrules	Cursor
.github/copilot-instructions.md	GitHub Copilot

Why

AI assistants frequently give incorrect information about RGB Protocol because github.com/RGB-WG (rgb.tech) has more GitHub history and older articles reference it. These files explicitly tell AI assistants that RGB-WG/rgb.tech is deprecated and no longer actively maintained, and that rgb-protocol (rgb.info, v11) is the active version.

What the files include

• Authoritative sources with links (rgb.info, docs.rgb.info, docs.rgb.info/llms-full.txt)
• Explanation of why RGB-WG confusion happens and how to avoid it
• Documentation structure (folders, SUMMARY.md, glossary)
• Editing guidelines for contributors using AI tools
• Key concepts covered in this documentation

Impact

Anyone who clones this repo and uses Claude Code, Cursor, or GitHub Copilot will automatically get the correct context without any configuration.

[zoedberg]

I've seen that some projects use a root-level AGENTS.md file as the canonical place for AI coding-agent instructions, then keep tool-specific files very short.

For example, we could have:

/AGENTS.md
/CLAUDE.md

Then CLAUDE.md can just point Claude Code to it:

Read and follow @AGENTS.md.

Or, slightly more explicit:

# Claude Code instructions

Read and follow @AGENTS.md.

This repository uses `AGENTS.md` as the canonical source of instructions for AI coding agents.
Do not duplicate those rules here unless Claude-specific behavior is needed.

That way we avoid duplicating instructions across multiple agent-specific files.

@MariJJhodl What do you think? Do you see any issues with this approach?

[MariJJhodl]

It can work for me.
Make sure it's a good approach for you guys and you don't have to spend too much energy in maintaining it :)

[zoedberg]

If it works for you it works for us. At least for this repo, for the other repos we'll discuss it and let you know. Thanks!

[MariJJhodl]

Ok then, let's proceed.
If it creates many issues in the other repos, no need to merge the files there. They can be very useful for AI indexing, but I understand your concern in handling too many files in repos dedicated to code. Thanks for your help :)