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/api-parameter-validation.test.ts

@@ -34,6 +34,10 @@ describe('API Parameter Validation', () => {
     })
   })
 
+  afterAll(async () => {
+    await brain.close()
+  })
+
   it('should use "where" parameter for metadata filtering', async () => {
     const results = await brain.find({
       where: { category: 'test-category' },