chore: organize solution into module folders (Core/Server/Drivers/Client/Tooling)

Group all 69 projects into category subfolders under src/ and tests/ so the
Rider Solution Explorer mirrors the module structure. Folders: Core, Server,
Drivers (with a nested Driver CLIs subfolder), Client, Tooling.

- Move every project folder on disk with git mv (history preserved as renames).
- Recompute relative paths in 57 .csproj files: cross-category ProjectReferences,
  the lib/ HintPath+None refs in Driver.Historian.Wonderware, and the external
  mxaccessgw refs in Driver.Galaxy and its test project.
- Rebuild ZB.MOM.WW.OtOpcUa.slnx with nested solution folders.
- Re-prefix project paths in functional scripts (e2e, compliance, smoke SQL,
  integration, install).

Build green (0 errors); unit tests pass. Docs left for a separate pass.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/Client/ZB.MOM.WW.OtOpcUa.Client.UI.Tests/BrowseTreeViewModelTests.cs

@@ -0,0 +1,155 @@
+using Shouldly;
+using Xunit;
+using ZB.MOM.WW.OtOpcUa.Client.UI.Services;
+using ZB.MOM.WW.OtOpcUa.Client.UI.Tests.Fakes;
+using ZB.MOM.WW.OtOpcUa.Client.UI.ViewModels;
+using BrowseResult = ZB.MOM.WW.OtOpcUa.Client.Shared.Models.BrowseResult;
+
+namespace ZB.MOM.WW.OtOpcUa.Client.UI.Tests;
+
+public class BrowseTreeViewModelTests
+{
+    private readonly SynchronousUiDispatcher _dispatcher;
+    private readonly FakeOpcUaClientService _service;
+    private readonly BrowseTreeViewModel _vm;
+
+    public BrowseTreeViewModelTests()
+    {
+        _service = new FakeOpcUaClientService
+        {
+            BrowseResults =
+            [
+                new BrowseResult("ns=2;s=Node1", "Node1", "Object", true),
+                new BrowseResult("ns=2;s=Node2", "Node2", "Variable", false)
+            ]
+        };
+        _dispatcher = new SynchronousUiDispatcher();
+        _vm = new BrowseTreeViewModel(_service, _dispatcher);
+    }
+
+    [Fact]
+    public async Task LoadRootsAsync_PopulatesRootNodes()
+    {
+        await _vm.LoadRootsAsync();
+
+        _vm.RootNodes.Count.ShouldBe(2);
+        _vm.RootNodes[0].DisplayName.ShouldBe("Node1");
+        _vm.RootNodes[1].DisplayName.ShouldBe("Node2");
+    }
+
+    [Fact]
+    public async Task LoadRootsAsync_BrowsesWithNullParent()
+    {
+        await _vm.LoadRootsAsync();
+
+        _service.BrowseCallCount.ShouldBe(1);
+        _service.LastBrowseParentNodeId.ShouldBeNull();
+    }
+
+    [Fact]
+    public void Clear_RemovesAllRootNodes()
+    {
+        _vm.RootNodes.Add(new TreeNodeViewModel("ns=2;s=X", "X", "Object", false, _service, _dispatcher));
+        _vm.Clear();
+
+        _vm.RootNodes.ShouldBeEmpty();
+    }
+
+    [Fact]
+    public async Task LoadRootsAsync_NodeWithChildren_HasPlaceholder()
+    {
+        await _vm.LoadRootsAsync();
+
+        var nodeWithChildren = _vm.RootNodes[0];
+        nodeWithChildren.HasChildren.ShouldBeTrue();
+        nodeWithChildren.Children.Count.ShouldBe(1);
+        nodeWithChildren.Children[0].IsPlaceholder.ShouldBeTrue();
+    }
+
+    [Fact]
+    public async Task LoadRootsAsync_NodeWithoutChildren_HasNoPlaceholder()
+    {
+        await _vm.LoadRootsAsync();
+
+        var leafNode = _vm.RootNodes[1];
+        leafNode.HasChildren.ShouldBeFalse();
+        leafNode.Children.ShouldBeEmpty();
+    }
+
+    [Fact]
+    public async Task TreeNode_FirstExpand_TriggersChildBrowse()
+    {
+        _service.BrowseResults =
+        [
+            new BrowseResult("ns=2;s=Parent", "Parent", "Object", true)
+        ];
+
+        await _vm.LoadRootsAsync();
+
+        // Reset browse results for child browse
+        _service.BrowseResults =
+        [
+            new BrowseResult("ns=2;s=Child1", "Child1", "Variable", false)
+        ];
+
+        var parent = _vm.RootNodes[0];
+        var initialBrowseCount = _service.BrowseCallCount;
+
+        parent.IsExpanded = true;
+
+        // Allow async operation to complete
+        await Task.Delay(50);
+
+        _service.BrowseCallCount.ShouldBe(initialBrowseCount + 1);
+        parent.Children.Count.ShouldBe(1);
+        parent.Children[0].DisplayName.ShouldBe("Child1");
+    }
+
+    [Fact]
+    public async Task TreeNode_SecondExpand_DoesNotBrowseAgain()
+    {
+        _service.BrowseResults =
+        [
+            new BrowseResult("ns=2;s=Parent", "Parent", "Object", true)
+        ];
+
+        await _vm.LoadRootsAsync();
+
+        _service.BrowseResults =
+        [
+            new BrowseResult("ns=2;s=Child1", "Child1", "Variable", false)
+        ];
+
+        var parent = _vm.RootNodes[0];
+        parent.IsExpanded = true;
+        await Task.Delay(50);
+
+        var browseCountAfterFirst = _service.BrowseCallCount;
+
+        parent.IsExpanded = false;
+        parent.IsExpanded = true;
+        await Task.Delay(50);
+
+        _service.BrowseCallCount.ShouldBe(browseCountAfterFirst);
+    }
+
+    [Fact]
+    public async Task TreeNode_IsLoading_TransitionsDuringBrowse()
+    {
+        _service.BrowseResults =
+        [
+            new BrowseResult("ns=2;s=Parent", "Parent", "Object", true)
+        ];
+
+        await _vm.LoadRootsAsync();
+
+        _service.BrowseResults = [];
+
+        var parent = _vm.RootNodes[0];
+        parent.IsExpanded = true;
+        await Task.Delay(50);
+
+        // After completion, IsLoading should be false
+        parent.IsLoading.ShouldBeFalse();
+    }
+}