Task #135 — update integration-test NodeIds for path-based scheme

7 integration tests in Server.Tests were left behind by the path-based
NodeId rename (#134). Each was constructing test NodeIds in the old
"FullReference" shape ("TestFolder.Var1", "raw.var", "AlphaFolder.Var1",
"plcaddr-temperature"), which the node manager no longer mints — the new
shape is `{driverId}/{folder-path}/{browseName}` per OPC UA Part 3 §5.2.2
NodeId immutability.

Fixed by re-deriving each test NodeId from the actual browse path the test
fixture's driver registers:

- OpcUaServerIntegrationTests: "TestFolder.Var1" → "fake/TestFolder/Var1"
- HistoryReadIntegrationTests (4 tests): "raw.var" → "history-driver/raw",
  "proc.var" → "history-driver/proc" (×2), "atTime.var" → "history-driver/atTime"
- MultipleDriverInstancesIntegrationTests: "AlphaFolder.Var1" →
  "alpha/AlphaFolder/Var1"; "BetaFolder.Var1" → "beta/BetaFolder/Var1"
- OpcUaEquipmentWalkerIntegrationTests: "plcaddr-temperature" →
  "galaxy-prod/warsaw/line-a/oven-3/Temperature" (the walker uses Tag.Name
  as the browseName; the FullReference lives in TagConfig but no longer
  surfaces in the NodeId path)

Server.Tests now 277/277 green excluding LiveLdap. Clears the regression
flagged during the #124 verification run.

tests/ZB.MOM.WW.OtOpcUa.Server.Tests/OpcUaServerIntegrationTests.cs

@@ -73,7 +73,10 @@ public sealed class OpcUaServerIntegrationTests : IAsyncLifetime
         using var session = await OpenSessionAsync();
 
         var nsIndex = (ushort)session.NamespaceUris.GetIndex("urn:OtOpcUa:fake");
-        var varNodeId = new NodeId("TestFolder.Var1", nsIndex);
+        // Path-based NodeId per #134 — `{driverId}/{folder-path}/{browseName}`. The driver-side
+        // FullReference ("TestFolder.Var1") is now decoupled from the NodeId so a backend rename
+        // doesn't shift the identifier seen by clients (OPC UA Part 3 §5.2.2 immutability).
+        var varNodeId = new NodeId("fake/TestFolder/Var1", nsIndex);
 
         var dv = session.ReadValue(varNodeId);
         dv.ShouldNotBeNull();