Function theme_engine_theme_load_builtin 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn theme_engine_theme_load_builtin(
    name: *const c_char,
    out_theme: *mut *mut ThemeEngineTheme,
) -> i32

Loads a built-in theme by name (for example "tokyonight-dark").

Returns status code and writes a new handle to out_theme on success.