/**
 * ASCII/Unicode sparkline renderer for the Bet 5 "save your first chart"
 * moment on the success outro.
 *
 * Takes a numeric series and maps it onto one of eight vertical-bar block
 * glyphs (U+2581..U+2588). Empty / single-point / degenerate series collapse
 * to a single middle-level glyph so the outro never shows a broken render.
 */
export interface SparklineOptions {
    /** Maximum characters to render. Long series are evenly downsampled. */
    maxWidth?: number;
}
/**
 * Render a numeric series as a sparkline. Returns an empty string for an
 * empty input (caller decides whether to show a placeholder).
 *
 * Negative values are clamped to the observed min so the glyph map stays
 * monotonic. NaN and non-finite values are dropped before rendering.
 */
export declare function renderSparkline(series: readonly number[], options?: SparklineOptions): string;
