docs+code: close Theme 1 — 24 design-doc / XML-doc drift findings

Doc/XML-comment drift + small adherence fixes across 17 modules. Highlights:
- Host-017: site CoordinatedShutdown ordering — SiteStreamGrpcServer gains
  CancelAllStreams() (refuse new streams, cancel active), wired into
  Program.cs site branch via ApplicationStopping.
- InboundAPI-021: ParentExecutionId now travels on RouteToGet/SetAttributes
  symmetric with RouteToCallRequest; RouteHelper stamps from _parentExecutionId.
- ClusterInfra-012: ClusterOptionsValidator now requires both seed nodes.
- Comm-018: SiteCommunicationActor.HeartbeatMessage.IsActive derived from
  cluster leader check (was hardcoded true).
- DM-020: reconciliation audit row attributes the current user, not prior deployer.
- SEL-019: EventLogPurgeService early-exits on standby via active-node check.
- Plus comment/XML-doc accuracy fixes across AuditLog, ConfigurationDatabase,
  NotificationOutbox, SiteRuntime, SiteCallAudit; doc refreshes for Component-
  Commons / -ManagementService / -CLI / -ExternalSystemGateway / -HealthMonitoring
  / -Transport / -ConfigurationDatabase; CD-023 index-name doc alignment.

11 new regression tests (RouteHelper x4, SiteStreamGrpcServer x2,
ClusterOptionsValidator x1, SiteCommunicationActor x1, DeploymentService x1,
EventLogPurgeService x3). Build clean (0 warnings); InboundAPI/Communication/
Host suites all green. README regenerated: 112 open (was 136).

code-reviews/DeploymentManager/findings.md

@@ -1012,8 +1012,8 @@ also produces an audit entry.
 |--|--|
 | Severity | Low |
 | Category | Documentation & comments |
-| Status | Open |
-| Location | `src/ScadaLink.DeploymentManager/DeploymentService.cs:683-686` |
+| Status | Resolved |
+| Location | `src/ScadaLink.DeploymentManager/DeploymentService.cs:698-712` |
 
 **Description**
 
@@ -1041,6 +1041,16 @@ Use `user` (the parameter on `DeployInstanceAsync`, threaded through
 `OriginalDeployer = prior.DeployedBy` in the detail object so the original
 attribution is preserved without misrepresenting who took the action.
 
+**Resolution (2026-05-28):** Threaded the `user` parameter from
+`DeployInstanceAsync` into `TryReconcileWithSiteAsync` as a new `currentUser`
+argument (consistent with the DeploymentManager-018 `forceEnabledState`
+parameter-threading pattern) and rewrote the audit call to log
+`currentUser` as the actor with `OriginalDeployer = prior.DeployedBy` carried
+in the detail object. Added test
+`DeployInstanceAsync_Reconciled_AuditAttributesCurrentUserNotPriorDeployer`
+that pins the new attribution and asserts the prior deployer is no longer used
+as the actor. Tests green (80/80 in DeploymentManager.Tests).
+
 ### DeploymentManager-021 — `ResolveSiteIdentifierAsync` silently substitutes the DB id when the site row is missing
 
 | | |