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/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Tests/Health/HostStatusAggregatorTests.cs

@@ -0,0 +1,137 @@
+using Shouldly;
+using Xunit;
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+using ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Health;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Tests.Health;
+
+/// <summary>
+///     Tests for <see cref="HostStatusAggregator"/> — the merge + diff logic for the
+///     transport entry plus per-platform probe entries that
+///     <c>IHostConnectivityProbe.GetHostStatuses()</c> surfaces.
+/// </summary>
+public sealed class HostStatusAggregatorTests
+{
+    private static HostConnectivityStatus Status(string host, HostState state) =>
+        new(host, state, DateTime.UtcNow);
+
+    [Fact]
+    public void Snapshot_Empty_WhenNothingTracked()
+    {
+        var agg = new HostStatusAggregator();
+        agg.Snapshot().ShouldBeEmpty();
+    }
+
+    [Fact]
+    public void Update_NewHost_FiresChange_PreviousIsUnknown()
+    {
+        var agg = new HostStatusAggregator();
+        var captured = new List<HostStatusChangedEventArgs>();
+        agg.OnHostStatusChanged += (_, e) => captured.Add(e);
+
+        agg.Update(Status("PlatformA", HostState.Running));
+
+        captured.Count.ShouldBe(1);
+        captured[0].HostName.ShouldBe("PlatformA");
+        captured[0].OldState.ShouldBe(HostState.Unknown);
+        captured[0].NewState.ShouldBe(HostState.Running);
+    }
+
+    [Fact]
+    public void Update_SameState_DoesNotFire()
+    {
+        var agg = new HostStatusAggregator();
+        agg.Update(Status("PlatformA", HostState.Running));
+
+        var captured = new List<HostStatusChangedEventArgs>();
+        agg.OnHostStatusChanged += (_, e) => captured.Add(e);
+
+        agg.Update(Status("PlatformA", HostState.Running));
+
+        captured.ShouldBeEmpty();
+    }
+
+    [Fact]
+    public void Update_StateTransition_FiresChangeWithCorrectPreviousAndNew()
+    {
+        var agg = new HostStatusAggregator();
+        agg.Update(Status("PlatformA", HostState.Running));
+
+        var captured = new List<HostStatusChangedEventArgs>();
+        agg.OnHostStatusChanged += (_, e) => captured.Add(e);
+
+        agg.Update(Status("PlatformA", HostState.Stopped));
+
+        captured.Count.ShouldBe(1);
+        captured[0].OldState.ShouldBe(HostState.Running);
+        captured[0].NewState.ShouldBe(HostState.Stopped);
+    }
+
+    [Fact]
+    public void Snapshot_ReflectsEveryUpsertedHost()
+    {
+        var agg = new HostStatusAggregator();
+        agg.Update(Status("Transport", HostState.Running));
+        agg.Update(Status("PlatformA", HostState.Running));
+        agg.Update(Status("PlatformB", HostState.Stopped));
+
+        var snap = agg.Snapshot();
+
+        snap.Count.ShouldBe(3);
+        snap.Select(s => s.HostName).OrderBy(x => x).ShouldBe(new[] { "PlatformA", "PlatformB", "Transport" });
+        snap.First(s => s.HostName == "PlatformB").State.ShouldBe(HostState.Stopped);
+    }
+
+    [Fact]
+    public void Update_HostNameComparison_IsCaseInsensitive()
+    {
+        var agg = new HostStatusAggregator();
+        var captured = new List<HostStatusChangedEventArgs>();
+        agg.OnHostStatusChanged += (_, e) => captured.Add(e);
+
+        agg.Update(Status("PlatformA", HostState.Running));
+        agg.Update(Status("platforma", HostState.Stopped)); // same host, different case
+
+        captured.Count.ShouldBe(2);
+        captured[1].OldState.ShouldBe(HostState.Running);
+        captured[1].NewState.ShouldBe(HostState.Stopped);
+        agg.Snapshot().Count.ShouldBe(1);
+    }
+
+    [Fact]
+    public void Remove_TrackedHost_ReturnsTrue_AndDropsFromSnapshot()
+    {
+        var agg = new HostStatusAggregator();
+        agg.Update(Status("PlatformA", HostState.Running));
+        agg.Remove("PlatformA").ShouldBeTrue();
+        agg.Snapshot().ShouldBeEmpty();
+    }
+
+    [Fact]
+    public void Remove_UnknownHost_ReturnsFalse()
+    {
+        var agg = new HostStatusAggregator();
+        agg.Remove("Nope").ShouldBeFalse();
+    }
+
+    [Fact]
+    public void ConcurrentUpdates_DoNotCorruptDictionary()
+    {
+        var agg = new HostStatusAggregator();
+        const int threadCount = 8;
+        const int updatesPerThread = 250;
+
+        var tasks = Enumerable.Range(0, threadCount).Select(t => Task.Run(() =>
+        {
+            for (var i = 0; i < updatesPerThread; i++)
+            {
+                var hostName = $"Host{(t * updatesPerThread + i) % 32}";
+                var state = i % 2 == 0 ? HostState.Running : HostState.Stopped;
+                agg.Update(Status(hostName, state));
+            }
+        })).ToArray();
+
+        Task.WaitAll(tasks);
+        agg.Snapshot().Count.ShouldBeLessThanOrEqualTo(32);
+    }
+}