Add CLAUDE.md with commit message rules

Author: darrenangle

CLAUDE.md

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+# Claude Code Rules for abide
+
+## Commit Messages
+
+**NEVER include Claude attribution in commit messages.** Do not add:
+- `Co-Authored-By: Claude <noreply@anthropic.com>`
+- `🤖 Generated with [Claude Code](https://claude.com/claude-code)`
+- Any other reference to Claude or AI generation
+
+Commit messages should be clean and professional, describing only what was changed and why.
+
+## Git Hooks
+
+A `commit-msg` hook is installed in `.git/hooks/` that will reject commits containing Claude attribution.