Add a GROUP matrix variable to valgrind and sanitizer test configurations with simple numeric values. Use matrix.GROUP in artifact names instead of sanitizing the descriptive NAME, which contains special characters. This is cleaner and more maintainable than string replacement logic. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>