/**
 * Dev-time boundary-shadowing diagnostic (#114).
 *
 * Detects when a non-boundary CSS rule at equal/higher specificity targets the
 * same properties as boundary output — the crown consumer bug where layout flips
 * at the wrong breakpoint while JS reports the right state.
 *
 * @module
 */
/** One property set emitted by a boundary for a given selector. */
export interface BoundaryRuleSlice {
    readonly selector: string;
    readonly properties: ReadonlySet<string>;
}
/**
 * Compare boundary-emitted CSS against foreign (non-\@quantize) CSS.
 * Returns human-readable warnings for shadowing rules.
 */
export declare function diagnoseBoundaryShadowing(boundaryCss: string, foreignCss: string, foreignFile: string): readonly string[];
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