fix: clear stale legacy preview route

scripts/build-area.js

@@ -584,7 +584,12 @@ function writeCesiumPreview(area, roadProvider) {
   const started = Date.now();
   const startedAt = new Date(started).toISOString();
   fs.mkdirSync(path.dirname(htmlPath), { recursive: true });
-  if (vehicleRoute) writeVehicleRoute(area, vehicleRoute);
+  if (vehicleRoute) {
+    writeVehicleRoute(area, vehicleRoute);
+  } else {
+    // Do not let a route from an earlier legacy preview survive into native output.
+    fs.rmSync(area.outputs.vehicleRoute, { force: true });
+  }
   const vehicleModelNames = writeVehicleModel(area);
   writeCesiumPreviewSupportFiles(path.dirname(htmlPath));
   const glbName = "package/manifest.json";