feat(sitecall-audit): carry + persist SourceNode end-to-end via cached telemetry

Site: site emitters of SiteCallOperational (ExternalSystemClient, the script-API
cached call path in ScriptRuntimeContext, CachedCallLifecycleBridge) inject
INodeIdentityProvider and stamp SourceNode = NodeName at construction.

OperationTrackingStore call site in CachedCallTelemetryForwarder now stamps
SourceNode too.

Central: SiteCallAuditRepository.UpsertAsync INSERT includes SourceNode in the
column list; conditional monotonic UPDATE uses
COALESCE(@SourceNode, SourceNode) so later packets cannot blank a previously-
stamped value. After this commit every SiteCalls row carries node-a/node-b in
SourceNode (subject to monotonic preservation).

tests/ScadaLink.SiteCallAudit.Tests/SiteCallAuditActorTests.cs

@@ -49,7 +49,8 @@ public class SiteCallAuditActorTests : TestKit, IClassFixture<MsSqlMigrationFixt
         string? lastError = null,
         DateTime? createdAtUtc = null,
         DateTime? updatedAtUtc = null,
-        bool terminal = false)
+        bool terminal = false,
+        string? sourceNode = null)
     {
         var created = createdAtUtc ?? DateTime.UtcNow;
         var updated = updatedAtUtc ?? created;
@@ -59,6 +60,7 @@ public class SiteCallAuditActorTests : TestKit, IClassFixture<MsSqlMigrationFixt
             Channel = "ApiOutbound",
             Target = "ERP.GetOrder",
             SourceSite = sourceSite,
+            SourceNode = sourceNode,
             Status = status,
             RetryCount = retryCount,
             LastError = lastError,
@@ -492,6 +494,67 @@ public class SiteCallAuditActorTests : TestKit, IClassFixture<MsSqlMigrationFixt
         Assert.Equal("corr-fault", response.CorrelationId);
     }
 
+    // ── SourceNode-stamping (Task 14): end-to-end actor → repo persistence ──
+
+    [SkippableFact]
+    public async Task UpsertSiteCallCommand_PersistsSourceNode_EndToEnd()
+    {
+        Skip.IfNot(_fixture.Available, _fixture.SkipReason);
+
+        // SourceNode-stamping (Task 14): an UpsertSiteCallCommand carrying
+        // SourceNode "node-a" must land in the SiteCalls row's SourceNode
+        // column unchanged — verifies the actor's mapping path does not
+        // strip the column AND the repository INSERT writes it.
+        var siteId = NewSiteId();
+        var id = TrackedOperationId.New();
+        var row = NewRow(id, siteId, status: "Submitted", sourceNode: "node-a");
+
+        await using var context = CreateContext();
+        var repo = new SiteCallAuditRepository(context);
+        var actor = CreateActor(repo);
+
+        actor.Tell(new UpsertSiteCallCommand(row), TestActor);
+        var reply = ExpectMsg<UpsertSiteCallReply>(TimeSpan.FromSeconds(10));
+        Assert.True(reply.Accepted);
+
+        await using var readContext = CreateContext();
+        var stored = await readContext.Set<SiteCall>()
+            .Where(s => s.TrackedOperationId == id)
+            .ToListAsync();
+        Assert.Single(stored);
+        Assert.Equal("node-a", stored[0].SourceNode);
+    }
+
+    [SkippableFact]
+    public async Task UpsertSiteCallCommand_NullSourceNode_PersistsNull()
+    {
+        Skip.IfNot(_fixture.Available, _fixture.SkipReason);
+
+        // Mirror of the above for unstamped packets — a command with null
+        // SourceNode persists NULL on the row rather than falling back to a
+        // placeholder. The first audit packet from a legacy host (or a node
+        // without INodeIdentityProvider wired) must NOT inject a fabricated
+        // value central-side.
+        var siteId = NewSiteId();
+        var id = TrackedOperationId.New();
+        var row = NewRow(id, siteId, status: "Submitted", sourceNode: null);
+
+        await using var context = CreateContext();
+        var repo = new SiteCallAuditRepository(context);
+        var actor = CreateActor(repo);
+
+        actor.Tell(new UpsertSiteCallCommand(row), TestActor);
+        var reply = ExpectMsg<UpsertSiteCallReply>(TimeSpan.FromSeconds(10));
+        Assert.True(reply.Accepted);
+
+        await using var readContext = CreateContext();
+        var stored = await readContext.Set<SiteCall>()
+            .Where(s => s.TrackedOperationId == id)
+            .ToListAsync();
+        Assert.Single(stored);
+        Assert.Null(stored[0].SourceNode);
+    }
+
     /// <summary>
     /// Test double whose <see cref="ISiteCallAuditRepository.QueryAsync"/> always
     /// throws — used to verify the query handler's failure projection produces a