/**
 * Build a proxy URL with query params, signing it when a secret is available.
 *
 * Used by embed handlers that inject proxy URLs into HTML/JSON responses.
 * When `secret` is set, URLs are HMAC-signed so clients can fetch them without
 * needing a page token. When it's undefined, URLs fall back to unsigned form
 * (which is only safe when the `withSigning` middleware has no secret either).
 */
export declare function buildProxyUrl(path: string, query: Record<string, unknown>, secret?: string): string;