/**
 * All of stdin, or '' when there is none to read.
 *
 * Claude Code writes the payload and closes the pipe at once. Run by hand from a
 * terminal there is no pipe, and run from something that leaves stdin open
 * without writing to it there would be nothing to wait for -- so a TTY reads
 * nothing, and a pipe that stays silent is given up on.
 */
export declare function readStdin(timeoutMs?: number): Promise<string>;