/**
 * DebugState — collision pairs, grid cells, velocities for debug rendering.
 * Only populated when config.debug is set. Tree-shaken in production.
 */
export interface DebugState {
    collisionPairs: ReadonlyArray<readonly [string, string]>;
    velocities: ReadonlyArray<{
        id: string;
        vx: number;
        vy: number;
    }>;
}