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>

src/Client/ZB.MOM.WW.OtOpcUa.Client.Shared/Models/ConnectionStateChangedEventArgs.cs

@@ -0,0 +1,23 @@
+namespace ZB.MOM.WW.OtOpcUa.Client.Shared.Models;
+
+/// <summary>
+///     Event data raised when the client connection state changes.
+/// </summary>
+public sealed class ConnectionStateChangedEventArgs : EventArgs
+{
+    public ConnectionStateChangedEventArgs(ConnectionState oldState, ConnectionState newState, string endpointUrl)
+    {
+        OldState = oldState;
+        NewState = newState;
+        EndpointUrl = endpointUrl;
+    }
+
+    /// <summary>The previous connection state.</summary>
+    public ConnectionState OldState { get; }
+
+    /// <summary>The new connection state.</summary>
+    public ConnectionState NewState { get; }
+
+    /// <summary>The endpoint URL associated with the state change.</summary>
+    public string EndpointUrl { get; }
+}