test(hygiene): close every brain the remaining suites create

id-normalization.test.ts's makeBrain() and degraded-reads-surfaced.test.ts's
per-test brains had nothing tracking them — both now use a describe-scoped
opened[] array drained by afterEach.

find-hybrid-filter-before-hydrate.test.ts had two beforeAll-built brains
(one per describe block) with no matching afterAll.

multi-process-safety.test.ts and plugin-autodetect.test.ts/plugin.test.ts
left a brain whose init() was expected to reject (a rejected init() still
registers the instance in Brainy's global instance registry — the
constructor does that unconditionally — so it still needs close() to
deregister, or the process-level shutdown hooks never see the registry go
idle for the rest of the run).

tests/integration/multi-process-safety.test.ts

@@ -107,7 +107,11 @@ describe('Multi-process safety + read-only mode', () => {
 
       const blocked = new Brainy({ requireSubtype: false, storage: { type: 'filesystem', path: dir } })
       await expect(blocked.init()).rejects.toThrow(/another writer holds/i)
-      // Don't track `blocked` for afterEach cleanup since init failed.
+      // A rejected init() still registered `blocked` in Brainy's global
+      // instance registry (the constructor does that unconditionally) — close()
+      // is safe to call even though init() never completed, and is what
+      // deregisters it (and, once idle, the process-level shutdown hooks).
+      await blocked.close().catch(() => {})
     })
 
     it('takes over a STALE foreign lock (dead PID + old heartbeat) and claims atomically', async () => {
@@ -151,6 +155,7 @@ describe('Multi-process safety + read-only mode', () => {
       const err: any = await blocked.init().catch((e) => e)
       expect(err.code).toBe('BRAINY_WRITER_LOCKED')
       expect(err.lockInfo?.pid).toBe(otherPid)
+      await blocked.close().catch(() => {})
     })
 
     it('release drains an in-flight heartbeat — no phantom lock re-created after unlink', async () => {