doc: generate llms.txt

[araujogui]

Related #59264

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.62%. Comparing base (3a53447) to head (c7f9ebd).
⚠️ Report is 9 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #62027      +/-   ##
==========================================
+ Coverage   89.60%   89.62%   +0.01%     
==========================================
  Files         706      706              
  Lines      219179   219179              
  Branches    41993    41995       +2     
==========================================
+ Hits       196400   196433      +33     
+ Misses      14675    14633      -42     
- Partials     8104     8113       +9     

see 31 files with indirect coverage changes

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[targos]

Is there any evidence that AI systems use it?

[araujogui]

Is there any evidence that AI systems use it?

Evidence is hard to find because training data pipelines are very opaque but some usage from ai providers I found:

https://code.claude.com/docs/llms.txt
https://ai.google.dev/api/llms.txt
https://microsoft.github.io/genaiscript/.well-known/llms.txt

[Copilot]

Pull request overview

This PR updates the Node.js core documentation build to also generate an out/doc/llms.txt artifact (related to #59264’s work on improving module descriptions for llms.txt in doc-kit tooling).

Changes:

• Extend doc-only to include out/doc/llms.txt as a produced documentation artifact.
• Add a new Makefile rule that runs @node-core/doc-kit with the llms-txt template to emit out/doc/llms.txt.

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