fix: Missing onCleanup, update gravity test (#1821)

Author: cieplypolar

apps/typegpu-docs/src/examples/tests/copy-error/index.ts

@@ -101,3 +101,11 @@ if (!table) {
 table.innerText = (input.getUint32(12) === result.getUint32(12))
   ? 'The bug DOES NOT occur on this device.'
   : 'The bug DOES occur on this device.';
+
+// #region Example controls and cleanup
+
+export function onCleanup() {
+  device?.destroy();
+}
+
+// #endregion

packages/typegpu/tests/examples/individual/gravity.test.ts

@@ -149,7 +149,8 @@ describe('gravity example', () => {
       }
 
       struct Camera_2 {
-        position: vec3f,
+        position: vec4f,
+        targetPos: vec4f,
         view: mat4x4f,
         projection: mat4x4f,
       }
@@ -201,7 +202,8 @@ describe('gravity example', () => {
       }
 
       struct Camera_5 {
-        position: vec3f,
+        position: vec4f,
+        targetPos: vec4f,
         view: mat4x4f,
         projection: mat4x4f,
       }