/** Filesystem-safe filename part: dots (and anything exotic) → dashes. */
export declare function sanitizeForFilename(part: string): string;
/** `Checkout--error-card-declined.png` for screen "Checkout", state "error.card.declined". */
export declare function pngFileName(screen: string, state: string): string;
/**
 * Render every screen × requiredState of the project to
 * `<outDir>/<screen>--<state>.png`. Returns the number of PNGs written.
 * Throws (never process.exit) with a descriptive message — including
 * PLAYWRIGHT_HINT when Playwright is missing.
 */
export declare function runPngExport(fileArg: string | undefined, outDir: string): Promise<number>;