End-of-day flatten exit: the position is flat from N minutes before the session close until the close. At close - N (resolved against the DATE's real close, so a half-day flattens early instead of being missed) it closes the position and cancels any resting entry; entries decided in the window are skipped as policy:eod_flat_window. A daily/hourly entry filling at the open is flattened the same session. A scheduled entry at or after close - N is refused at compile. Attach it as its own exit. Equity only: refused for crypto (24h sessions have no close).