- Add comprehensive C++ naming rules for typephp_, php::, typephp_<project>, and php_ prefixes
- Document ABI boundaries and symbol collision prevention guidelines
- Update MIXED_CPP_PHP.md with cross-reference to new naming convention document
- Clarify php_ prefix usage for user callable ABI mapping vs internal helpers
- Add project-specific namespace details for typephp_<target> data declarations
- Include code review checklist for naming convention compliance
- Reference new documentation in main README table of contents
