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-planner-door.test.ts

@@ -23,7 +23,7 @@
  * against the adjacency before it is believed, so a not-serving graph refuses
  * loudly instead of answering `[]` as truth.
  */
-import { describe, it, expect, beforeAll, vi } from 'vitest'
+import { describe, it, expect, beforeAll, afterAll, vi } from 'vitest'
 import { Brainy } from '../../src/brainy'
 import { NounType, VerbType } from '../../src/types/graphTypes'
 import { generateTestVector } from '../helpers/test-factory'
@@ -56,6 +56,10 @@ describe('find(): the optional planner door', () => {
     }
   })
 
+  afterAll(async () => {
+    await brain.close()
+  })
+
   /** Install a planner door for one call, then remove it. */
   const withDoor = async <T>(
     door: (...a: any[]) => Promise<any>,