Constant CLOSE_WAIT_TIMEOUT 

pub const CLOSE_WAIT_TIMEOUT: Duration;

Default upper bound on close() wait-for-exit. After this elapses, the child is SIGKILL’d. 5s is generous for a CLI that’s draining in-flight turns; tests that want to verify the kill path drive against a process that ignores stdin EOF. Public so a consumer timing a wait over a session’s teardown can derive it from this budget rather than guess.