/**
 * Content hash for optimistic concurrency control on agent writes.
 *
 * The operation router records the hash of each cell's content as the agent
 * last saw it (from read results); write operations carry that hash and the
 * applier — the live UI when connected, the headless handler otherwise —
 * rejects the write if the cell's current content no longer matches. This is
 * compare-and-swap at the point of application: immune to autosave latency
 * and to browser/server clock skew (which rule out timestamp-based checks).
 *
 * MUST stay in sync with lib/cellHash.ts (frontend copy).
 */
export declare function hashCellContent(content: string): string;