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/relationship-intelligence.test.ts

@@ -59,7 +59,8 @@ describe('Relationship Intelligence', () => {
     await brain.init()
   })
 
-  afterEach(() => {
+  afterEach(async () => {
+    await brain.close()
     if (fs.existsSync(testDir)) {
       fs.rmSync(testDir, { recursive: true })
     }