/**
 * A low-level utility for observing DOM attributes on custom elements
 * without coupling to Lit's reactive property/rendering lifecycle.
 *
 * Handles:
 * - Accumulating `observedAttributes` across multiple decorator calls
 * - Routing `attributeChangedCallback` to per-attribute handler functions
 * - Chaining with Lit's own `attributeChangedCallback` for its reactive properties
 * - Inheritance-safe handler maps (own map per constructor)
 *
 * @example
 * ```ts
 * // Inside a decorator:
 * observeAttributes(MyElement, {
 *   'aria-labelledby': (host, oldVal, newVal) => { ... },
 *   'gds-aria-labelledby': (host, oldVal, newVal) => { ... },
 * })
 * ```
 */
type AttrHandler = (host: any, oldValue: string | null, newValue: string | null) => void;
/**
 * Register one or more non-reactive attribute observers on a custom element class.
 *
 * Safe to call multiple times on the same constructor — handlers accumulate
 * and the prototype patching is idempotent.
 *
 * @param ctor The custom element constructor (class) to patch.
 * @param handlers A record mapping attribute names to handler functions.
 */
export declare function observeAttributes(ctor: any, handlers: Record<string, AttrHandler>): void;
export {};