/**
 * Copy text to the clipboard.
 * - Uses the async Clipboard API when available (requires a secure context)
 * - Falls back to `document.execCommand('copy')` otherwise, so copying still
 *   works over plain HTTP (e.g. internal test environments)
 * - Never throws; resolves to whether the copy succeeded
 */
export declare function copyToClipboard(text: string): Promise<boolean>;