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

tests/integration/find-*.test.ts and tests/unit/brainy/find*.test.ts each
opened one or more Brainy instances (via beforeAll/beforeEach) and never
closed them — the leaked instance's cadence timer stays armed for the rest
of the single-forked vitest run and keeps narrating into every later file.

find-unified-integration.test.ts was a real bug, not just a missing hook:
its afterAll called a no-op TestCleanup().cleanup() (nothing was ever
registered with it) and then discarded the brain reference with
`brain = null` — the brain was never actually closed.

tests/integration/find-fields-projection.test.ts

@@ -19,7 +19,7 @@
  * index-served (a body field, or a bucketed timestamp), exactly the owing rows
  * are read and the rest are still served from the index.
  */
-import { describe, it, expect, beforeAll, vi } from 'vitest'
+import { describe, it, expect, beforeAll, afterAll, vi } from 'vitest'
 import { Brainy } from '../../src/brainy'
 import { NounType } from '../../src/types/graphTypes'
 import { generateTestVector } from '../helpers/test-factory'
@@ -59,6 +59,10 @@ describe('find/get({ fields }) — projection', () => {
     await brain.flush()
   })
 
+  afterAll(async () => {
+    await brain.close()
+  })
+
   /** Count canonical record reads for one call. */
   const countingReads = async <R>(body: () => Promise<R>): Promise<{ out: R; reads: number }> => {
     const spy = vi.spyOn(brain as any, 'batchGet')