refactor(scenes): the director needs no viewer for its camera

Camera-gesture listeners attach to the engine's canvas and the
interaction availability check tolerates a missing viewer, so a director
built on an engine alone places, flies and stops scene cameras.

src/scenes/director.js

@@ -113,7 +113,7 @@ export class SceneDirector {
     this._interactionTransitions = 0;
     this._interactions = createSceneInteractions(viewer, {
       available: () =>
-        !this._destroyed && !this._running && !this.viewer.trackedEntity,
+        !this._destroyed && !this._running && !this.viewer?.trackedEntity,
       execute: (action, signal) =>
         this._trackWork(this._executeInteraction(action, signal)),
     });
@@ -132,12 +132,12 @@ export class SceneDirector {
     };
     this._cameraHandoffUnsubscribe =
       styleManager.subscribeCameraHandoff?.(yieldCamera);
-    const canvas = viewer.scene?.canvas;
+    const canvas = engine?.host.canvas ?? viewer?.scene?.canvas;
     for (const event of ['pointerdown', 'wheel'])
-      canvas?.addEventListener(event, yieldCamera, { passive: true });
+      canvas?.addEventListener?.(event, yieldCamera, { passive: true });
     this._removeCameraInput = () => {
       for (const event of ['pointerdown', 'wheel'])
-        canvas?.removeEventListener(event, yieldCamera);
+        canvas?.removeEventListener?.(event, yieldCamera);
     };
 
     /** @type {boolean} True while a scene run is in progress */

src/scenes/director.test.mjs

@@ -1597,3 +1597,27 @@ test('camera refusal starts no authored frame or playback clock', async () => {
     assert.deepEqual(viewer.flights, []);
   } finally { restore(); }
 });
+
+test('scene placement, flights and stop run on a globe engine without a viewer', async () => {
+  const restore = installSceneRuntime();
+  try {
+    const engine = createFakeEngine();
+    const director = new SceneDirector(null, fakeStyleManager(), fakeDataManager(), { engine });
+    const pose = { lat: 27.95, lon: 85.95, alt: 4200, heading: 40, pitch: -25, roll: 0 };
+    assert.equal(director._setCameraView(pose), true);
+    const placed = engine.camera.pose().cartographic;
+    assert.ok(Math.abs(placed.height - 4200) < 1e-6);
+    const flying = director._flyCamera({ ...pose, alt: 6000 }, 0.2, { cancelled: false });
+    const [flight] = engine.fake.callsOf('camera.flyTo').at(-1).args;
+    assert.equal(flight.easing, 'cubicInOut');
+    engine.fake.frames(20, 16);
+    await flying;
+    assert.ok(Math.abs(engine.camera.height() - 6000) < 1e-6);
+    director.stopScene('test');
+    assert.ok(engine.fake.callsOf('camera.cancelFlight').length >= 2);
+    director.destroy();
+    await director._destroyPromise;
+  } finally {
+    restore();
+  }
+});