test(hygiene): close every brain the integration suite creates

Each file opened a Brainy in beforeAll/beforeEach (or a single it()) and
never closed it. related-verb-array.test.ts and vfs-containment-batched.test.ts
were real bugs: their afterAll discarded the brain with `brain = null as any`
without ever calling close() first.

tests/integration/related-verb-array.test.ts

@@ -30,6 +30,7 @@ describe('related() with a verb-type array returns every requested type', () =>
   })
 
   afterAll(async () => {
+    await brain.close()
     brain = null as any
   })