docs: add CLAUDE.md with comment guidance for Claude Code

[bobluppes]

Summary

• Add a CLAUDE.md file at the repo root with guidance for Claude Code sessions working in this project.
• Comments should only call out non-obvious rationale or design choices, not restate what the code already makes clear; prefer self-documenting code via clear names and proper abstraction.
• Public API documentation comments should never leak implementation details — document behavior and usage, not internals.

Test plan

• N/A — documentation-only change for agent guidance, no code or build changes.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.71%. Comparing base (600b02a) to head (e58b546).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #404   +/-   ##
=======================================
  Coverage   99.71%   99.71%           
=======================================
  Files          60       60           
  Lines        2823     2823           
  Branches      151      151           
=======================================
  Hits         2815     2815           
  Misses          8        8           

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