docs(dn): record task 8 fix round 4

.superpowers/sdd/2026-09-18-hybrid-delivery-note-ingestion/task-8-report.md

@@ -258,3 +258,45 @@ concurrent legacy run proceeded instead of returning `batch_locked`.
 - The additive staged-ingestion migration remains a release prerequisite; it
   must be applied before deployment. No production apply or PocketBase writes
   were performed.
+
+## Fix Round 4
+
+Status: complete.
+
+### RED evidence
+
+The new fencing regressions recorded **17 intended failures** before the
+implementation: protected business mutations could occur outside the lease
+transaction, allowing a reclaimed owner to write after ownership loss.
+
+### GREEN evidence
+
+- Focused fencing, lock, page, promotion, legacy-run, staged-run, tick, and
+  assembly suites: **164 passed** across 9 files.
+- `npm run typecheck`: passed.
+- `git diff --check`: passed.
+- No production PocketBase writes were performed.
+
+### Fixes and files
+
+- `src/lib/dn-pipeline/batch-mutations.ts` and `test-batch.ts` provide the
+  PocketBase batch mutation adapter and test fixture.
+- `src/lib/dn-pipeline/lock.ts` exposes the fenced lease mutation helpers and
+  rejects SDKs without transactional batch support.
+- `src/lib/dn-pipeline/page-store.ts`, `promote.ts`, `run.ts`, and
+  `run-staged.ts` route protected writes through the lease fence.
+- `src/app/api/dn-batches/tick/route.ts` and
+  `src/app/api/dn-batches/[id]/assembly/route.ts` use the same protected path.
+- Regression coverage is in `batch-mutations.test.ts`, `fencing.test.ts`, and
+  the focused lock/page/promotion/run/staged/tick/assembly test updates.
+
+### Decision
+
+Each business mutation shares a PocketBase batch transaction with the current
+lease-record update. If the lease fence is stale or reclaimed, PocketBase
+rejects the transaction and rolls back the business mutation.
+
+### Code commit
+
+`b5ba219d10cb2760c4776fe6751b8800e67684c6` —
+`fix(dn): transactionally fence protected writes`