/**
 * Resolve the active variant key for a block, based on its manifest variants and content.
 *
 * Fallback chain:
 * 1) content.variant (preferred)
 * 2) content.layout (legacy blog listing support)
 * 3) manifest.defaultVariant
 * 4) First key in manifest.variants
 */
export declare function resolveVariantKey(manifest: {
    variants?: Record<string, unknown> | null;
    defaultVariant?: string | null;
}, content: Record<string, unknown>): string | null;
