Add CLAUDE.md documentation and update .gitignore

This adds comprehensive documentation for Claude Code to work more effectively in this repository, including architecture details, testing conventions, and development workflows. Also adds .claude/ to .gitignore to exclude Claude Code configuration.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: oschwald

.gitignore

@@ -1,6 +1,7 @@
 *~
 *.egg
 .eggs
+.claude/
 .idea
 build
 .coverage