/**
 * Pure transforms for the `GuidePanel` article index — grouping (#25) and
 * filtering (#26). Kept framework-free so the index logic is unit-testable
 * without rendering the panel (mirrors `pagination.engine` / `planner.bucket`).
 */
/** A registered article as surfaced to the panel index. */
export interface IndexArticle {
    id: string;
    title: string;
    /** Optional section label; `undefined` means the ungrouped block. */
    group?: string;
}
/** One section of the grouped index. */
export interface ArticleSection {
    /** The section's group label, or `undefined` for the headerless ungrouped block. */
    group: string | undefined;
    articles: IndexArticle[];
}
/**
 * Group articles into sections keyed by `group`, in first-occurrence order over
 * the (insertion-ordered) input. Articles without a `group` collect into one
 * headerless section, positioned where its first ungrouped article appears.
 * When no article sets a `group`, the result is a single ungrouped section —
 * i.e. a flat list.
 */
export declare function groupArticles(articles: IndexArticle[]): ArticleSection[];
/** Whether any section carries a real group label (drives grouped vs. flat rendering). */
export declare function hasNamedGroups(sections: ArticleSection[]): boolean;
/**
 * Filter articles by a case-insensitive substring match on the title. A blank
 * query returns the input unchanged. Whitespace around the query is ignored.
 */
export declare function filterArticles(articles: IndexArticle[], query: string): IndexArticle[];