refactor(centralui): complete cycle fallback + polish in ExecutionTree

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

@@ -184,6 +184,49 @@ public class ExecutionTreeTests : BunitContext
         Assert.Equal(1, CountOccurrences(cut.Markup, $"data-test=\"tree-node-{b}\""));
     }
 
+    [Fact]
+    public void ToggleExpand_CollapsesAndReExpandsChildSubtree()
+    {
+        // root → child → grandchild. Clicking the root's toggle collapses its
+        // subtree (the child node disappears); clicking it again re-expands.
+        var root = Guid.Parse("aaaaaaaa-3333-3333-3333-333333333333");
+        var child = Guid.Parse("bbbbbbbb-3333-3333-3333-333333333333");
+        var grandchild = Guid.Parse("cccccccc-3333-3333-3333-333333333333");
+        var nodes = new List<ExecutionTreeNode>
+        {
+            Node(root, null),
+            Node(child, root),
+            Node(grandchild, child),
+        };
+
+        var cut = Render<ExecutionTree>(p => p
+            .Add(c => c.Nodes, nodes)
+            .Add(c => c.ArrivedFromExecutionId, root));
+
+        // All nodes start expanded — the whole chain is visible on arrival.
+        Assert.Contains($"data-test=\"tree-node-{child}\"", cut.Markup);
+        Assert.Contains($"data-test=\"tree-node-{grandchild}\"", cut.Markup);
+
+        var toggle = cut.Find($"[data-test=\"tree-toggle-{root}\"]");
+        Assert.Equal("true", toggle.GetAttribute("aria-expanded"));
+
+        // Collapse: the child (and its descendants) must disappear.
+        toggle.Click();
+        Assert.DoesNotContain($"data-test=\"tree-node-{child}\"", cut.Markup);
+        Assert.DoesNotContain($"data-test=\"tree-node-{grandchild}\"", cut.Markup);
+        Assert.Equal(
+            "false",
+            cut.Find($"[data-test=\"tree-toggle-{root}\"]").GetAttribute("aria-expanded"));
+
+        // Re-expand: the child subtree reappears.
+        cut.Find($"[data-test=\"tree-toggle-{root}\"]").Click();
+        Assert.Contains($"data-test=\"tree-node-{child}\"", cut.Markup);
+        Assert.Contains($"data-test=\"tree-node-{grandchild}\"", cut.Markup);
+        Assert.Equal(
+            "true",
+            cut.Find($"[data-test=\"tree-toggle-{root}\"]").GetAttribute("aria-expanded"));
+    }
+
     private static int CountOccurrences(string haystack, string needle)
     {
         int count = 0, idx = 0;