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.Historian.Wonderware/Backend/AlarmHistorianWriteOutcome.cs

@@ -0,0 +1,19 @@
+namespace ZB.MOM.WW.OtOpcUa.Driver.Historian.Wonderware.Backend
+{
+    /// <summary>
+    ///     Per-event outcome from <see cref="IAlarmHistorianWriteBackend.WriteBatchAsync"/>.
+    ///     Sidecar-local twin of <c>Core.AlarmHistorian.HistorianWriteOutcome</c> (the
+    ///     sidecar runs net48 and cannot reference the net10 Core project; the IPC
+    ///     contract narrows this to <c>bool</c> per slot, so the lmxopcua-side consumer
+    ///     widens that back into the trinary outcome at the IPC boundary in PR B.4).
+    /// </summary>
+    public enum AlarmHistorianWriteOutcome
+    {
+        /// <summary>Event accepted by the historian. Drop from the store-and-forward queue.</summary>
+        Ack,
+        /// <summary>Transient failure (server busy, disconnected, timeout). Leave queued; retry on next drain tick.</summary>
+        RetryPlease,
+        /// <summary>Permanent failure (malformed event, unrecoverable SDK error). Move to dead-letter on the lmxopcua side.</summary>
+        PermanentFail,
+    }
+}