fix: import dedup off-switch honesty + brain-owned lifecycle for the background pass

The post-import background deduplication pass (a merge-DELETE writer,
debounced ~5 minutes after import) had four lifecycle defects:

- enableDeduplication: false did not gate the background schedule — an
  import that explicitly opted out could still have entities auto-removed
  minutes later. The flag now gates both the inline and background passes.
- Each import() constructed its own coordinator-owned deduplicator, so the
  debounce never spanned imports (N imports = N delete timers). The brain
  now owns a single lazy instance (getBackgroundDeduplicator).
- close() never cancelled pending dedup; a delete pass could fire against
  a closed brain. close() now cancels it first.
- The 5-minute timer held the process open (exit-hang class); now unref'd.

Four regression tests pin the contract (background-dedup-lifecycle);
import guides document that false disables both passes.

RELEASES.md

@@ -10,6 +10,28 @@ Full auto-generated changelog: `CHANGELOG.md` · Releases: https://github.com/so
 
 ---
 
+## v8.8.1 — 2026-07-18 (the import dedup off-switch is now honest + lifecycle-safe)
+
+The post-import background deduplication pass (a merge-DELETE writer that runs ~5 minutes
+after an import, merging entities judged duplicates by id / name / vector similarity) had
+three lifecycle defects, all fixed:
+
+- **`enableDeduplication: false` now actually disables it.** The background pass was
+  scheduled unconditionally — an import that explicitly opted out could still have
+  entities auto-removed 5 minutes later. The flag now gates BOTH the inline merge and
+  the background pass (regression-pinned).
+- **One deduplicator per brain, owned by the brain.** Each `import()` call constructed its
+  own coordinator + deduplicator, so the "debounced" timer never actually debounced across
+  imports (N imports = N delete timers). The brain now owns a single instance — the
+  debounce genuinely spans imports — and `close()` cancels pending work, so a delete pass
+  can never fire against a closed brain.
+- **The 5-minute timer is unref'd** — a pending pass no longer holds the process open
+  (the exit-hang class; this timer had escaped the earlier sweep).
+
+Retention note for keep-everything deployments: with `enableDeduplication: false` on
+import calls and `retention: 'all'` in config, no engine path removes records
+automatically.
+
 ## v8.8.0 — 2026-07-17 (OS-limit detection for pool-scale deployments)
 
 Small minor: brains now detect the two OS limits that bite at pool scale and warn **before**