feat(arena): add deterministic headless RL environments

src/aircraft/controller.ts

@@ -334,6 +334,25 @@ export class AircraftController {
     return { ...this.current };
   }
 
+  /** Restore a trusted JSON snapshot for deterministic environment checkpointing. */
+  restore(snapshot: AircraftControllerSnapshot): void {
+    const numeric = Object.entries(snapshot)
+      .filter(([, value]) => typeof value === "number")
+      .every(([, value]) => Number.isFinite(value));
+    const envelope = this.options.envelope;
+    if (
+      !numeric || (snapshot.mode !== "manual" && snapshot.mode !== "assisted") ||
+      snapshot.lat < envelope.minLat || snapshot.lat > envelope.maxLat ||
+      snapshot.lng < envelope.minLng || snapshot.lng > envelope.maxLng ||
+      snapshot.altitudeM < envelope.minAltitudeM || snapshot.altitudeM > envelope.maxAltitudeM ||
+      snapshot.speedMps < this.options.minimumSpeedMps ||
+      snapshot.speedMps > this.options.maximumSpeedMps ||
+      !Number.isSafeInteger(snapshot.elapsedSteps) || snapshot.elapsedSteps < 0
+    ) throw new RangeError("aircraft snapshot is incompatible or invalid");
+    Object.assign(this.current, snapshot);
+    this.accumulator = 0;
+  }
+
   reset(): void {
     this.accumulator = 0;
     Object.assign(this.current, this.options.initialPosition, {