feat: add subtle full-body sheep walking motion

tests/rain-gear.test.ts

@@ -11,6 +11,7 @@ import { Vector3 } from 'three';
 
 test('idle breathing carries the coat and hood without lifting the feet or changing the umbrella grip', async () => {
   const [model, umbrella, raincoat] = await Promise.all(['red-sheep', 'umbrella', 'raincoat'].map(asset));
+  raincoat.name = 'TestRaincoat';
   const sheep = createSheep(model, { umbrella, raincoat });
   sheep.setEquipment(true, true, true);
   const body = model.getObjectByName('Body')!, head = model.getObjectByName('Head')!;
@@ -26,6 +27,15 @@ test('idle breathing carries the coat and hood without lifting the feet or chang
   sheep.pose('idle', 0, false, 2);
   assert.ok(arm.quaternion.angleTo(grip) < 1e-8);
   assert.ok(foot.getWorldPosition(new Vector3()).distanceTo(footPosition) < 1e-8);
+  const remote = sheep.clone();
+  remote.pose('idle', 0, false, 0);
+  remote.pose('idle', 0, false, 1);
+  const remoteCoat = remote.group.getObjectByName('TestRaincoat')!;
+  const remoteCoatPosition = remoteCoat.position.clone();
+  sheep.pose('idle', 0, true, 3);
+  remote.pose('idle', 0, false, 1);
+  assert.deepEqual(remoteCoat.position, remoteCoatPosition, 'local walking cannot change a remote coat pivot');
+  remote.dispose();
   sheep.dispose();
 });