fix(adminui): S7 typed page no longer wipes Tags on save

- S7DriverPage.FormModel now preserves Tags through Form ↔ Options
  translation (was hard-coding Tags = [] on every save, silently
  destroying any tag list that operators had configured).
- Add FormModel_RoundTrip tests for OpcUaClient and Historian
  mirror classes — both were translating Options ↔ form-model
  entirely untested.
- Surface S7 Tags in the round-trip test so this regression
  can't reach merge again.

tests/Server/ZB.MOM.WW.OtOpcUa.AdminUI.Tests/OpcUaClientDriverPageFormSerializationTests.cs

@@ -1,7 +1,9 @@
+using System.Collections.Generic;
 using System.Text.Json;
 using System.Text.Json.Serialization;
 using Shouldly;
 using Xunit;
+using ZB.MOM.WW.OtOpcUa.AdminUI.Components.Pages.Clusters.Drivers;
 using ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient;
 
 namespace ZB.MOM.WW.OtOpcUa.AdminUI.Tests;
@@ -79,4 +81,76 @@ public sealed class OpcUaClientDriverPageFormSerializationTests
         back.ShouldNotBeNull();
         back.ProbeTimeoutSeconds.ShouldBe(20);
     }
+
+    [Fact]
+    public void FormModel_RoundTrip_PreservesAllFields()
+    {
+        // Construct options with non-default values for every editable property plus
+        // non-empty EndpointUrls and UnsMappingTable — both are "read-only" in the form
+        // but must survive the FormModel translation unchanged.
+        var endpointUrls = new List<string> { "opc.tcp://primary:4840", "opc.tcp://backup:4840" };
+        var unsMappingTable = new Dictionary<string, string>
+        {
+            ["Line1/"] = "Site/Area1/Line1",
+            ["Line2/"] = "Site/Area1/Line2",
+        };
+
+        var original = new OpcUaClientDriverOptions
+        {
+            EndpointUrl              = "opc.tcp://fallback:4840",
+            EndpointUrls             = endpointUrls,
+            ApplicationUri           = "urn:test:OtOpcUa:GatewayClient",
+            SessionName              = "TestSession",
+            SecurityMode             = OpcUaSecurityMode.SignAndEncrypt,
+            SecurityPolicy           = OpcUaSecurityPolicy.Basic256Sha256,
+            AuthType                 = OpcUaAuthType.Username,
+            Username                 = "opcuser",
+            Password                 = "p@ssw0rd",
+            UserCertificatePath      = @"C:\certs\user.pfx",
+            UserCertificatePassword  = "certpass",
+            PerEndpointConnectTimeout = TimeSpan.FromSeconds(4),
+            Timeout                  = TimeSpan.FromSeconds(12),
+            SessionTimeout           = TimeSpan.FromSeconds(150),
+            KeepAliveInterval        = TimeSpan.FromSeconds(7),
+            ReconnectPeriod          = TimeSpan.FromSeconds(8),
+            AutoAcceptCertificates   = true,
+            BrowseRoot               = "i=85",
+            MaxDiscoveredNodes       = 3000,
+            MaxBrowseDepth           = 5,
+            TargetNamespaceKind      = OpcUaTargetNamespaceKind.SystemPlatform,
+            UnsMappingTable          = unsMappingTable,
+            ProbeTimeoutSeconds      = 25,
+        };
+
+        var form = OpcUaClientDriverPage.OpcUaClientFormModel.FromRecord(original);
+        var result = form.ToRecord();
+
+        result.EndpointUrl.ShouldBe("opc.tcp://fallback:4840");
+        result.EndpointUrls.Count.ShouldBe(2);
+        result.EndpointUrls[0].ShouldBe("opc.tcp://primary:4840");
+        result.EndpointUrls[1].ShouldBe("opc.tcp://backup:4840");
+        result.ApplicationUri.ShouldBe("urn:test:OtOpcUa:GatewayClient");
+        result.SessionName.ShouldBe("TestSession");
+        result.SecurityMode.ShouldBe(OpcUaSecurityMode.SignAndEncrypt);
+        result.SecurityPolicy.ShouldBe(OpcUaSecurityPolicy.Basic256Sha256);
+        result.AuthType.ShouldBe(OpcUaAuthType.Username);
+        result.Username.ShouldBe("opcuser");
+        result.Password.ShouldBe("p@ssw0rd");
+        result.UserCertificatePath.ShouldBe(@"C:\certs\user.pfx");
+        result.UserCertificatePassword.ShouldBe("certpass");
+        result.PerEndpointConnectTimeout.ShouldBe(TimeSpan.FromSeconds(4));
+        result.Timeout.ShouldBe(TimeSpan.FromSeconds(12));
+        result.SessionTimeout.ShouldBe(TimeSpan.FromSeconds(150));
+        result.KeepAliveInterval.ShouldBe(TimeSpan.FromSeconds(7));
+        result.ReconnectPeriod.ShouldBe(TimeSpan.FromSeconds(8));
+        result.AutoAcceptCertificates.ShouldBeTrue();
+        result.BrowseRoot.ShouldBe("i=85");
+        result.MaxDiscoveredNodes.ShouldBe(3000);
+        result.MaxBrowseDepth.ShouldBe(5);
+        result.TargetNamespaceKind.ShouldBe(OpcUaTargetNamespaceKind.SystemPlatform);
+        result.UnsMappingTable.Count.ShouldBe(2);
+        result.UnsMappingTable["Line1/"].ShouldBe("Site/Area1/Line1");
+        result.UnsMappingTable["Line2/"].ShouldBe("Site/Area1/Line2");
+        result.ProbeTimeoutSeconds.ShouldBe(25);
+    }
 }