/**
 * Applies the "previously" block to the current game state,
 * reconstructing what the full previous state would have been.
 * Deep merge to avoid overwriting nested fields.
 *
 * @param currentState - The current parsed state.
 * @param previously - The "previously" delta block from GSI, parsed.
 * @returns - The reconstructed state. */
export declare function applyDelta<T extends Object>(currentState: T, previously: T): T;