feat(ui): show SourceNode under SourceSiteId in audit log detail popup

The audit log drilldown drawer (and the execution-tree node-detail modal,
which shares this component) now renders the SourceNode field directly
under SourceSiteId so provenance reads 'site → node → instance → script'
in declared order. Two focused tests pin the field's presence in both
populated and null cases plus the inter-field ordering.

src/ScadaLink.CentralUI/Components/Audit/AuditEventDetail.razor

@@ -28,6 +28,9 @@
     <dt class="col-4 text-muted fw-normal">SourceSiteId</dt>
     <dd class="col-8" data-test="field-SourceSiteId">@(Event.SourceSiteId ?? "—")</dd>
 
+    <dt class="col-4 text-muted fw-normal">SourceNode</dt>
+    <dd class="col-8" data-test="field-SourceNode">@(Event.SourceNode ?? "—")</dd>
+
     <dt class="col-4 text-muted fw-normal">SourceInstanceId</dt>
     <dd class="col-8" data-test="field-SourceInstanceId">@(Event.SourceInstanceId ?? "—")</dd>
 

tests/ScadaLink.CentralUI.Tests/Components/Audit/AuditEventDetailTests.cs

@@ -81,6 +81,44 @@ public class AuditEventDetailTests : BunitContext
         Assert.Contains("2026-05-20T12:30:45", cut.Markup);
     }
 
+    [Fact]
+    public void RendersSourceNodeField_BetweenSiteAndInstance()
+    {
+        // SourceNode is rendered as a sibling row directly under SourceSiteId
+        // so the popup reads "site → node → instance → script" in provenance
+        // order. Populated case.
+        var ev = MakeEvent() with { SourceNode = "node-a" };
+
+        var cut = Render<AuditEventDetail>(p => p.Add(c => c.Event, ev));
+
+        Assert.Contains("data-test=\"field-SourceNode\"", cut.Markup);
+        Assert.Contains("node-a", cut.Markup);
+
+        // Ordering: SourceSiteId appears before SourceNode, which appears
+        // before SourceInstanceId.
+        var siteIdx = cut.Markup.IndexOf("data-test=\"field-SourceSiteId\"", StringComparison.Ordinal);
+        var nodeIdx = cut.Markup.IndexOf("data-test=\"field-SourceNode\"", StringComparison.Ordinal);
+        var instanceIdx = cut.Markup.IndexOf("data-test=\"field-SourceInstanceId\"", StringComparison.Ordinal);
+        Assert.True(siteIdx > 0 && nodeIdx > siteIdx && instanceIdx > nodeIdx,
+            $"Expected SourceSiteId < SourceNode < SourceInstanceId; got {siteIdx}, {nodeIdx}, {instanceIdx}");
+    }
+
+    [Fact]
+    public void RendersSourceNodeField_AsDashWhenNull()
+    {
+        // Null SourceNode (e.g. central direct-write row pre-feature, or a
+        // reconciled row from a retired node) renders as the em-dash, same
+        // convention as the sibling provenance fields.
+        var ev = MakeEvent();   // SourceNode left at default null
+        Assert.Null(ev.SourceNode);
+
+        var cut = Render<AuditEventDetail>(p => p.Add(c => c.Event, ev));
+
+        Assert.Contains("data-test=\"field-SourceNode\"", cut.Markup);
+        // The field is present and renders the em-dash placeholder.
+        Assert.Contains(">—<", cut.Markup);
+    }
+
     [Fact]
     public void ErrorSection_RendersWhenErrorPresent()
     {