test(globe): mover coverage on both engines; pickable: false honoured

Review of Tasks 2 and 4:
- A contract check draws, on both engines: an atlas cell switch, a
  rotation of π (a half-white cell flips from above to below the
  centre), scale 2 (about four times the area), scaleByDistance past
  `far` (about a quarter), setCount shrinking the set, depth modes for
  sprites 30 km under the ground ('always' and a disableWithinM past the
  camera draw), a point with its dark outline, and a glTF model
  (airplane.glb, minimumPixelSize 80, colorBlend replace) in magenta.
  'normal' and a 10 m disableWithinM hide the buried sprite on Navara;
  Cesium's billboards are not occluded by the app's photoreal tiles
  (globe hidden; measured), so those two are asserted on Navara only.
- pickable: false: Cesium's GPU pick sees every primitive, so the
  picker drops picks (and drill entries) of a set created with
  pickable: false; Navara only registers pickable sets. The contract's
  click check now clicks a pickable: false sprite on both engines.
- Navara resolves a GPU answer's batch id to the pick id when Navara
  answers (the pick's own frame), not when the engine's click consumes
  it: a set that reuses the instance in between still yields the
  instance that was under the pointer.

Contract: Cesium 70/70, Navara 76/76.

src/globe/cesium/movers.test.mjs

@@ -240,6 +240,7 @@ test('a pick of a billboard or point names its set and instance', async () => {
   assert.deepEqual(identify({ primitive: second, id: 25544 }), {
     owner: 'sats',
     instance: 1,
+    pickable: false,
   });
   assert.equal(identify({ primitive: {}, id: 'x' }), null);
   set.destroy();