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/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Galaxy/Health/HostConnectivityForwarder.cs

@@ -0,0 +1,58 @@
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Logging.Abstractions;
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Health;
+
+/// <summary>
+///     Pushes the synthetic top-level transport-health entry into the
+///     <see cref="HostStatusAggregator"/>. Each driver instance has one entry under its
+///     <c>MxAccess.ClientName</c> reflecting the gateway transport state — useful for
+///     dashboards that want a single "Galaxy is up" signal independent of any individual
+///     platform's ScanState.
+/// </summary>
+/// <remarks>
+///     The eventual production source for this signal is the gateway's <c>StreamSessionHealth</c>
+///     RPC (mxaccessgw issue gw-6). Until that ships, the driver-side reconnect supervisor
+///     (PR 4.5) calls <see cref="SetTransport"/> on transport state transitions:
+///     <see cref="HostState.Running"/> when the gw session re-Registers, <see cref="HostState.Stopped"/>
+///     when the supervisor moves to <c>TransportLost</c>. The forwarder is intentionally
+///     stateless beyond the cached client name + last-pushed value so the supervisor can
+///     drive it without any back-pressure plumbing.
+/// </remarks>
+public sealed class HostConnectivityForwarder : IDisposable
+{
+    private readonly string _clientName;
+    private readonly HostStatusAggregator _aggregator;
+    private readonly ILogger _logger;
+    private bool _disposed;
+
+    public HostConnectivityForwarder(string clientName, HostStatusAggregator aggregator, ILogger? logger = null)
+    {
+        ArgumentException.ThrowIfNullOrWhiteSpace(clientName);
+        _clientName = clientName;
+        _aggregator = aggregator ?? throw new ArgumentNullException(nameof(aggregator));
+        _logger = logger ?? NullLogger.Instance;
+    }
+
+    /// <summary>
+    ///     Push a transport state into the aggregator. Idempotent at the aggregator layer —
+    ///     repeated calls with the same state don't fan out duplicate transitions.
+    /// </summary>
+    public void SetTransport(HostState state)
+    {
+        ObjectDisposedException.ThrowIf(_disposed, this);
+        var status = new HostConnectivityStatus(_clientName, state, DateTime.UtcNow);
+        _aggregator.Update(status);
+        _logger.LogDebug(
+            "GalaxyDriver transport state for {ClientName}: {State}",
+            _clientName, state);
+    }
+
+    public void Dispose()
+    {
+        // No-op today; reserved for the eventual gw-6 StreamSessionHealth consumer that
+        // will own a long-running task this method tears down.
+        _disposed = true;
+    }
+}