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/Core/ZB.MOM.WW.OtOpcUa.Core.Abstractions/IReadable.cs

@@ -0,0 +1,25 @@
+namespace ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+
+/// <summary>
+///     Driver capability for on-demand reads. Required for any driver whose nodes are
+///     readable from OPC UA clients (essentially all of them — every committed v2 driver
+///     implements this).
+/// </summary>
+/// <remarks>
+///     Reads are idempotent — Polly retry pipelines can safely retry on transient failures
+///     (per <c>docs/v2/plan.md</c> decisions #34 and #44).
+/// </remarks>
+public interface IReadable
+{
+    /// <summary>
+    ///     Read a batch of attributes by their full driver-side reference.
+    ///     Returns one snapshot per requested reference, in the same order.
+    /// </summary>
+    /// <remarks>
+    ///     Per-reference failures should be reported via the snapshot's <see cref="DataValueSnapshot.StatusCode"/>
+    ///     (Bad-coded), not as exceptions. The whole call should throw only if the driver itself is unreachable.
+    /// </remarks>
+    Task<IReadOnlyList<DataValueSnapshot>> ReadAsync(
+        IReadOnlyList<string> fullReferences,
+        CancellationToken cancellationToken);
+}