Error handling

Many WUI operations report failure through bool and an error value:

if (!window->init("Application", {-1, -1, 800, 600}, wui::window_style::frame)) {
    std::cerr << window->get_error().str() << '\n';
}

Check a control's get_error() after loading images or constructing resources. error::is_ok() checks the status; str() formats the component and message. Theme/locale helpers also expose their load errors, and name-based loading accepts an error& argument.

Do not interpret this as a guarantee that C++ exceptions can never occur: allocation, user callbacks and some supporting APIs may throw. The WASM build explicitly enables exception support. Handle application failures at the appropriate boundary.