OptionalcallsignWaypoint callsign / label.
Optionallink0 = waypoint (b-m-p-w), 1 = control point (b-m-p-c).
OptionalpointWaypoint position, delta-encoded from the event anchor.
OptionaluidWaypoint UID (the builder synthesizes one from the event UID + index when absent).
Route waypoint/control point link.