chore: Add CLAUDE.md file

[SpyZzey]

Description

Claude Code only supports a CLAUDE.md file. This PR adds it and references the other steering files in it.

Related links, issue #, if available: n/a

How has this been tested?

Review checklist

The following items are to be evaluated by the author(s) and the reviewer(s).

Correctness

• Changes include appropriate documentation updates.
• Changes are backward-compatible if not indicated, see CONTRIBUTING.md.
• Changes do not include unsupported browser features, see CONTRIBUTING.md.
• Changes were manually tested for accessibility, see accessibility guidelines.

Security

• If the code handles URLs: all URLs are validated through the checkSafeUrl function.

Testing

• Changes are covered with new/existing unit tests?
• Changes are covered with new/existing integration tests?

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.41%. Comparing base (4187eac) to head (2d39dc1).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4504   +/-   ##
=======================================
  Coverage   97.41%   97.41%           
=======================================
  Files         933      933           
  Lines       29595    29595           
  Branches    10756    10757    +1     
=======================================
  Hits        28831    28831           
+ Misses        757      716   -41     
- Partials        7       48   +41     

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