EDGE with memory: true on the one close where fire holds after arm held on an earlier close, then disarmed. USE WHEN an event must follow a precondition — price re-enters a band after leaving it (arm=outside, fire=inside), first touch of a level after being clear of it, a rising edge of any condition (arm=not(c), fire=c). arm wins if both are true on one close; if either side has no value the result has none and the latch keeps its state. Never reset by positions. Children are inline conditions or condition_refs; it cannot hold a schedule or a stop/target. DO NOT USE for a plain level — use 'compare'.