getNearestReady

R74.3 Issue 3: the readiness gate for "Navigate Closest". FALSE while routed distances are still in flight; flips TRUE once enough rows (NEAREST_READY_THRESHOLD, capped to total list size) have reached a terminal state. The fragment binds this to button enabled/alpha/label so the user can't tap-and-route on a still-Mercator-ordered list (the cross-floor bug from R74.2 field testing).