/**
 * Head manager component that updates document.title and meta tags on route changes.
 * This component subscribes to route loader changes and updates the document head
 * with SEO metadata for client-side navigation.
 *
 * Features:
 * - Updates document.title based on seoMeta.title
 * - Creates/updates meta tags for description, keywords, robots
 * - Manages Open Graph tags for social media sharing
 * - Manages Twitter card tags
 * - Handles JSON-LD structured data
 * - Preserves Serverless rendering tags on hydration
 * - Avoids duplicate meta tags
 * - Handles edge cases: undefined/null metadata, inaccessible document.head, multiple instances
 *
 * **Important**: Place this component at the root level of your application, inside the RouterProvider.
 * Only one instance should be mounted per application.
 *
 * @returns {null} This component doesn't render anything
 *
 * @example
 * // Basic usage with RouterProvider
 * import { RuntimeHeadManager, RuntimeWebRouterProvider } from '@worktif/runtime';
 *
 * function App({ router }) {
 *   return (
 *     <>
 *       <RuntimeHeadManager />
 *       <YourAppContent />
 *     </>
 *   );
 * }
 *
 * @example
 * // Complete setup with runtimeRouter
 * import { runtimeRouter, RuntimeHeadManager, RuntimeWebRouterProvider } from '@worktif/runtime';
 *
 * const router = runtimeRouter({
 *   router: [
 *     {
 *       path: '/',
 *       element: <HomePage />,
 *       runtimeAsync: [
 *         async () => ({ homeData: await fetchHomeData() })
 *       ]
 *     }
 *   ],
 *   defaults: {}
 * });
 *
 * function App() {
 *   return (
 *     <>
 *       <RuntimeHeadManager />
 *       <Outlet />
 *     </>
 *   );
 * }
 *
 * @example
 * // The head manager automatically updates meta tags when navigating
 * // If your route loader returns SEO metadata like this:
 * // { internal: { seoMeta: { title: 'Product Page', description: '...' } } }
 * //
 * // The head manager will automatically:
 * // 1. Update document.title to 'Product Page'
 * // 2. Update meta description tag
 * // 3. Update Open Graph tags
 * // 4. Update Twitter card tags
 * // 5. Update JSON-LD structured data
 */
export declare function RuntimeHeadManager(): null;
