/**
 * Focusable elements inside a container, including those nested in the shadow
 * roots of child components (the header and input controls live in their own
 * shadow trees, so a plain querySelectorAll would miss them).
 */
export declare function getFocusableElements(container: HTMLElement): HTMLElement[];
/** The deepest active element, walking down through nested shadow roots. */
export declare function getActiveElement(): HTMLElement;
/**
 * Keeps Tab and Shift+Tab cycling within the container. Call from a keydown
 * handler when the key is Tab.
 */
export declare function trapFocus(event: KeyboardEvent, container: HTMLElement): void;