Add comprehensive reflection documentation to cheatsheet.md covering type
inspection, object methods, Type_Info, function introspection, system
introspection, and Dynamic_Object reflection. Add missing global reflection
functions (type_name, is_type, function_exists, get_functions, get_objects,
type, dump_system, dump_object) and is_type_arithmetic to the Doxygen
prelude docs. Include a thorough test exercising all documented features.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
