Function register_builtin_components 

pub extern "C" fn register_builtin_components() -> ComponentLibrary

Register the 52 built-in HTML element components.

This is an extern "C" function pointer compatible with RegisterComponentLibraryFnType, so it can be passed directly to AppConfig::add_component_library().

Called once during AppConfig::create() — the framework dogfoods its own component registration system for builtins.