fix(concurrency/lifetime): close Theme 5 — 10 concurrency / DI / scope findings

Concurrency hazards, DI lifetime hygiene, and one verify-only confirmation
across 8 modules. Highlights:

Concurrency:
- CentralUI-030: SandboxConsoleCapture writes routed through WriteSynchronized
  locking on the captured StringWriter — intra-script Task fan-out can no
  longer corrupt the per-call buffer.
- Commons-021: ExternalCallResult.Response now backed by Lazy<dynamic?>
  (ExecutionAndPublication) — no more benign double-parse race.
- CD-017: DeploymentManagerRepository.DeleteDeploymentRecordAsync now takes
  an expected RowVersion and seeds entry.OriginalValues so EF emits
  DELETE ... WHERE Id=@id AND RowVersion=@prior; stale RowVersion now
  throws DbUpdateConcurrencyException instead of silent overwrite.
- Transport-009: AuditCorrelationContext.BundleImportId backed by
  AsyncLocal<Guid?> so concurrent imports get per-logical-call isolation
  (was a scoped instance shared via AuditService across runs).

DI / lifetime:
- AuditLog-003: All 3 AuditLog actor handlers switched to CreateAsyncScope
  + await using — async EF disposal no longer swallowed.
- AuditLog-007: INodeIdentityProvider resolution standardised on
  GetRequiredService<>() (was mixed with GetService<>()).
- AuditLog-011: AddAuditLogHealthMetricsBridge guarded by sentinel
  descriptor check — calling twice no longer double-registers the hosted
  service.

Shutdown / supervision:
- SiteCallAudit-002: AkkaHostedService adds a CoordinatedShutdown
  cluster-leave task (drain-site-call-audit-singleton) that issues a
  bounded GracefulStop(10s) so failover waits for in-flight upserts.

Registration safety:
- NS-020: AkkaHostedService now guards NotificationForwarder S&F
  registration with _notificationDeliveryHandlerRegistered + throws
  InvalidOperationException on double-register to make the regression loud.

VERIFY-only closures:
- NotifOutbox-005: Confirmed already closed by CD-015 fix (ac96b83) —
  NotificationOutboxRepository.InsertIfNotExistsAsync uses the same
  raw-SQL IF NOT EXISTS + 2601/2627 swallow pattern; race eliminated.

5+ new regression tests (CentralUI sandbox WhenAll, ExternalCallResult
64-reader Barrier, AuditLog DI idempotency, RowVersion stale-throw,
SiteCallAudit-002 shutdown drain). Build clean; affected suites all green.
README regenerated: 65 open (was 75).

code-reviews/NotificationOutbox/findings.md

@@ -8,7 +8,7 @@
 | Last reviewed | 2026-05-28 |
 | Reviewer | claude-agent |
 | Commit reviewed | `1eb6e97` |
-| Open findings | 10 |
+| Open findings | 9 |
 
 ## Summary
 
@@ -237,9 +237,11 @@ _Unresolved._
 |--|--|
 | Severity | Medium |
 | Category | Concurrency & thread safety |
-| Status | Open |
+| Status | Resolved |
 | Location | `src/ScadaLink.NotificationOutbox/NotificationOutboxActor.cs:127-132` (caller); root cause in `src/ScadaLink.ConfigurationDatabase/Repositories/NotificationOutboxRepository.cs:33-45` |
 
+**Resolution (2026-05-28):** Closed by CD-015 — `NotificationOutboxRepository.InsertIfNotExistsAsync` (commit `ac96b83`) is now a single-statement `IF NOT EXISTS ... INSERT` via `ExecuteSqlInterpolatedAsync` with a `SqlException` filter swallowing duplicate-key violations (`2601`/`2627`) as a no-op (`return false`). The check-then-act window is eliminated; the at-least-once handoff contract holds and the actor's `PipeTo` success/failure projection no longer surfaces a permanent PK-violation back to the site. Verified in `src/ScadaLink.ConfigurationDatabase/Repositories/NotificationOutboxRepository.cs:51-103`.
+
 **Description**
 
 `HandleSubmit` → `PersistAsync` calls `repository.InsertIfNotExistsAsync(notification)`
@@ -271,10 +273,6 @@ and ack-back does not produce a permanent re-forward loop — but the cleanest f
 remains the CD-015 raw-SQL `IF NOT EXISTS … INSERT` with `2601/2627` catch in
 `NotificationOutboxRepository`.
 
-**Resolution**
-
-_Unresolved._
-
 ### NotificationOutbox-006 — `ResolveAdapters` rebuilds the `NotificationType → adapter` dictionary on every dispatch sweep
 
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