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/Runtime/IGalaxyDataWriter.cs

@@ -0,0 +1,33 @@
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Runtime;
+
+/// <summary>
+///     Driver-side seam for batched writes. Production implementation routes by
+///     <see cref="SecurityClassification"/>: SecuredWrite / VerifiedWrite go through
+///     <c>MxCommandKind.WriteSecured</c>, everything else through
+///     <c>MxGatewaySession.WriteAsync</c>. Tests substitute a fake to record routing
+///     decisions without touching real gw infrastructure.
+/// </summary>
+public interface IGalaxyDataWriter
+{
+    /// <summary>
+    ///     Write each <paramref name="writes"/> entry; return one
+    ///     <see cref="WriteResult"/> per request entry, in input order. Implementations
+    ///     MUST return the same length as the input — partial-tag failures are encoded
+    ///     as Bad-status results, not omitted.
+    /// </summary>
+    /// <param name="writes">Pairs of full reference + value to write.</param>
+    /// <param name="securityResolver">
+    ///     Maps a full reference to its discovered <see cref="SecurityClassification"/>
+    ///     so the writer can route SecuredWrite / VerifiedWrite tags through the
+    ///     <c>WriteSecured</c> command instead of <c>Write</c>. Returns
+    ///     <see cref="SecurityClassification.FreeAccess"/> when the tag isn't tracked
+    ///     (the safest default — non-secured Write).
+    /// </param>
+    /// <param name="cancellationToken">Aborts the in-flight batch.</param>
+    Task<IReadOnlyList<WriteResult>> WriteAsync(
+        IReadOnlyList<WriteRequest> writes,
+        Func<string, SecurityClassification> securityResolver,
+        CancellationToken cancellationToken);
+}