/**
 * The upgrade nudge.
 *
 * Publishing is deliberately never gated on engine age — a floor there could only ever be "the
 * newest engine" (the deploy workflow writes no floor, the manifest parser defaults an absent one
 * to the current version, and that workflow runs nightly), and blocking at publish is the worst
 * moment to ask anyway: the creator is finished and wants to ship.
 *
 * So the prompt lives where acting on it is cheap — during development, before there is anything
 * to lose by rebuilding.
 */
/** Nothing to say: either the project is current, or we could not find out. */
export type EngineUpdateNotice = string | null;
/**
 * Compare two `3.<build>` engine versions.
 *
 * Returns null when either side is unparseable, which the caller treats as "say nothing" rather
 * than "out of date" — an unrecognised version is not evidence of anything, and a nudge that
 * fires on every run is a nudge people learn to ignore.
 */
export declare function isOlderEngine(projectVersion: string, currentVersion: string): boolean | null;
/**
 * The line to print, or null to stay quiet.
 *
 * Quiet is the default for everything except a confirmed newer engine: unknown versions, equal
 * versions, and a project somehow ahead of the manifest all produce nothing.
 */
export declare function engineUpdateNotice(projectVersion: string, currentVersion: string | null | undefined): EngineUpdateNotice;