fix(flights): start new aircraft at their delayed display position

The fleet renders behind real time, so a newly seen aircraft is displayed at its fix projected back to that delayed time. Its billboard was created at the raw fix instead, so it appeared ahead of where the next fleet tick put it and then jumped back about one render delay of travel before moving forward.

src/layers/flights/snapshotRenderer.js

@@ -179,8 +179,14 @@ export function createFlightSnapshotRenderer({
         // as the enrichment path — the class's GLB/scale may have changed.
         if (prevMeta?.klass !== meta.klass) rendering._syncModelToClass(icao24);
       } else {
+        // Start where the fleet pass will draw it: the fleet renders behind
+        // real time, so a fresh contact's displayed position is its fix
+        // projected back to that delayed time. Creating it at the raw fix drew
+        // it ahead until the next fleet tick snapped it back.
+        const displayed =
+          motion._deadReckon(icao24, new Cesium.Cartesian3()) || position;
         const bb = flightState._billboardCollection.add({
-          position,
+          position: displayed,
           image: aircraftIcon(rendering._iconKind(icao24, meta.klass)),
           width: isTracked ? 24 : 20,
           height: isTracked ? 24 : 20,