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.Shared.Tests/Fakes/FakeSubscriptionAdapter.cs

@@ -0,0 +1,111 @@
+using Opc.Ua;
+using ZB.MOM.WW.OtOpcUa.Client.Shared.Adapters;
+
+namespace ZB.MOM.WW.OtOpcUa.Client.Shared.Tests.Fakes;
+
+/// <summary>
+/// Test double for <see cref="ISubscriptionAdapter" /> used to drive monitored-item behavior in shared-client tests.
+/// </summary>
+internal sealed class FakeSubscriptionAdapter : ISubscriptionAdapter
+{
+    private readonly
+        Dictionary<uint, (NodeId NodeId, Action<string, DataValue>? DataCallback, Action<EventFieldList>? EventCallback
+            )> _items = new();
+
+    private uint _nextHandle = 100;
+    /// <summary>
+    /// Gets a value indicating whether the fake subscription has been deleted.
+    /// </summary>
+    public bool Deleted { get; private set; }
+
+    /// <summary>
+    /// Gets a value indicating whether a condition refresh was requested by the client under test.
+    /// </summary>
+    public bool ConditionRefreshCalled { get; private set; }
+
+    /// <summary>
+    /// Gets or sets a value indicating whether condition refresh should throw to simulate unsupported servers.
+    /// </summary>
+    public bool ThrowOnConditionRefresh { get; set; }
+    public int AddDataChangeCount { get; private set; }
+    public int AddEventCount { get; private set; }
+    public int RemoveCount { get; private set; }
+
+    /// <summary>
+    ///     Gets the handles of all active items.
+    /// </summary>
+    public IReadOnlyCollection<uint> ActiveHandles => _items.Keys.ToList();
+
+    /// <inheritdoc />
+    public uint SubscriptionId { get; set; } = 42;
+
+    /// <inheritdoc />
+    public Task<uint> AddDataChangeMonitoredItemAsync(NodeId nodeId, int samplingIntervalMs,
+        Action<string, DataValue> onDataChange, CancellationToken ct)
+    {
+        AddDataChangeCount++;
+        var handle = _nextHandle++;
+        _items[handle] = (nodeId, onDataChange, null);
+        return Task.FromResult(handle);
+    }
+
+    /// <inheritdoc />
+    public Task RemoveMonitoredItemAsync(uint clientHandle, CancellationToken ct)
+    {
+        RemoveCount++;
+        _items.Remove(clientHandle);
+        return Task.CompletedTask;
+    }
+
+    /// <inheritdoc />
+    public Task<uint> AddEventMonitoredItemAsync(NodeId nodeId, int samplingIntervalMs, EventFilter filter,
+        Action<EventFieldList> onEvent, CancellationToken ct)
+    {
+        AddEventCount++;
+        var handle = _nextHandle++;
+        _items[handle] = (nodeId, null, onEvent);
+        return Task.FromResult(handle);
+    }
+
+    /// <inheritdoc />
+    public Task ConditionRefreshAsync(CancellationToken ct)
+    {
+        ConditionRefreshCalled = true;
+        if (ThrowOnConditionRefresh)
+            throw new InvalidOperationException("Condition refresh not supported");
+        return Task.CompletedTask;
+    }
+
+    /// <inheritdoc />
+    public Task DeleteAsync(CancellationToken ct)
+    {
+        Deleted = true;
+        _items.Clear();
+        return Task.CompletedTask;
+    }
+
+    /// <summary>
+    /// Clears tracked monitored items when the fake subscription is disposed by the client under test.
+    /// </summary>
+    public void Dispose()
+    {
+        _items.Clear();
+    }
+
+    /// <summary>
+    ///     Simulates a data change notification for testing.
+    /// </summary>
+    public void SimulateDataChange(uint handle, DataValue value)
+    {
+        if (_items.TryGetValue(handle, out var item) && item.DataCallback != null)
+            item.DataCallback(item.NodeId.ToString(), value);
+    }
+
+    /// <summary>
+    ///     Simulates an event notification for testing.
+    /// </summary>
+    public void SimulateEvent(uint handle, EventFieldList eventFields)
+    {
+        if (_items.TryGetValue(handle, out var item) && item.EventCallback != null) item.EventCallback(eventFields);
+    }
+}