// Dynamic menu loader.
// Fetches data for groups declared with empty children in navigation.json
// and injects them into side-nav after it is ready.
//
// Imported non-blocking from index.html — does not delay routing.
//
// Example usage:
//   const nav = document.querySelector('side-nav')
//   await nav.ready
//   nav.setGroupChildren('My Group', [{ label: 'Item', href: '#/route', icon: 'icon' }])