meta: ignore AI assistants files

[mcollina]

• Add CLAUDE.md and AGENTS.md to .gitignore under a new AI assistants section
• Exclude them from markdown linting in Makefile via $(filter-out ...)
• Exclude them from ESLint markdown processing in eslint.config.mjs

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.63%. Comparing base (61db260) to head (13c64d0).
⚠️ Report is 9 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #62612   +/-   ##
=======================================
  Coverage   89.63%   89.63%           
=======================================
  Files         708      708           
  Lines      220383   220383           
  Branches    42269    42273    +4     
=======================================
+ Hits       197539   197541    +2     
- Misses      14712    14722   +10     
+ Partials     8132     8120   -12     

see 32 files with indirect coverage changes

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[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/72547/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/72885/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/72976/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/72985/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/73024/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/73040/