/** Safely run `querySelector`; invalid selectors return `null`. */
export declare function querySelectorSafe(root: ParentNode, selector: string): HTMLElement | null;
/** Safely run `querySelectorAll`; invalid selectors return `[]`. */
export declare function querySelectorAllSafe(root: ParentNode, selector: string): HTMLElement[];
/** Slugify heading text for generated fragment IDs. */
export declare function slugifyHeadingText(text: string): string;
/**
 * Assign a unique `id` when missing, avoiding collisions with `usedIds` and the document.
 *
 * @remarks
 * Existing IDs are left untouched and recorded in `usedIds`. Generated IDs use
 * `base`, `base-2`, … until free.
 */
export declare function ensureUniqueHeadingId(heading: HTMLElement, usedIds: Set<string>, isTaken?: (id: string) => boolean): string;
/** Viewport Y where a heading counts as active (`scrollOffset` below the scroll root top). */
export declare function trackingLineY(scrollRoot: HTMLElement | Window, scrollOffset: number): number;
/** Scroll so `heading` sits `scrollOffset` below the scroll root's visible top. */
export declare function scrollHeadingIntoView(heading: HTMLElement, scrollRoot: HTMLElement | Window, scrollOffset: number, behavior: ScrollBehavior): void;