Add CLAUDE.md with comprehensive codebase documentation for AI assistants (#91)

Documents the module structure, $PSBPreference config system, public
API,
build workflows, task dependency system, CI/CD setup, code conventions,
and guidance specific to AI-assisted development in this repository.

https://claude.ai/code/session_018vQunv4wiTuk8WCkXCPfHn

Co-authored-by: Claude <noreply@anthropic.com>

Author: HeyItsGilbert