docs: add CLAUDE.md with dev context and coding guidelines reference

[zeevdr]

Summary

• Adds CLAUDE.md so Claude Code and contributors have the tech stack, key commands, and project layout at a glance when working in this repo.
• Links to the shared coding guidelines in the main repo rather than duplicating them here.

Test plan

• Verify CLAUDE.md renders correctly on GitHub
• Confirm commands in the quick-reference match the current Makefile

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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