/**
 * Resolve an element's effective language from the `lang` attribute,
 * following HTML's inheritance rules, and notify on changes.
 *
 * Returns:
 *   - a BCP 47 tag, e.g. "en-GB"
 *   - ""        -> lang="" was set: language is explicitly UNKNOWN. Stop walking.
 *   - undefined -> no lang anywhere. Let Intl use the runtime default.
 */
export declare function resolveLang(el: Element): string | undefined;
/** Convert to something safe to hand to Intl.* constructors. */
export declare function toIntlLocale(lang: string | undefined): string | undefined;
type Listener = () => void;
/**
 * Subscribe to `lang` changes anywhere in the light DOM.
 *
 * KNOWN LIMITATION: MutationObserver on `document` does not see mutations
 * inside shadow roots. A `lang` changed on an element inside another
 * component's shadow DOM will not trigger updates. Initial resolution is
 * still correct; only live updates are missed.
 */
export declare function onLangChange(listener: Listener): () => void;
export {};