test: remaining xUnit1051/1031/1030, CS8602/8604, CS0618, CS0219, CS0649, NU1510 fixes (lmxopcua#725)

Awaited deadline oracles get the runner token; sync-over-async tests made async;
nullable child models asserted via ShouldNotBeNull() return values; obsolete SDK
ctors replaced with the telemetry overloads; dead locals/fixture and the redundant
DI PackageReference removed. No suppressions.

Claude-Session: https://claude.ai/code/session_01GT67AEHd2Acv1YPwGfXEoV

tests/Client/ZB.MOM.WW.OtOpcUa.Client.Shared.Tests/Adapters/DefaultSubscriptionAdapterTests.cs

@@ -15,7 +15,7 @@ public class DefaultSubscriptionAdapterTests
     [Fact]
     public async Task DeleteAsync_detaches_the_subscription_from_its_session_once()
     {
-        var subscription = new Subscription();
+        var subscription = new Subscription(ClientTelemetry.Context);
         var detached = new List<Subscription>();
         var adapter = new DefaultSubscriptionAdapter(subscription, (s, _) =>
         {
@@ -34,7 +34,7 @@ public class DefaultSubscriptionAdapterTests
     public void Dispose_detaches_the_subscription_from_its_session()
     {
         var detached = 0;
-        var adapter = new DefaultSubscriptionAdapter(new Subscription(), (_, _) =>
+        var adapter = new DefaultSubscriptionAdapter(new Subscription(ClientTelemetry.Context), (_, _) =>
         {
             Interlocked.Increment(ref detached);
             return Task.CompletedTask;
@@ -49,7 +49,7 @@ public class DefaultSubscriptionAdapterTests
     [Fact]
     public async Task A_failing_detach_does_not_throw_from_DeleteAsync()
     {
-        var adapter = new DefaultSubscriptionAdapter(new Subscription(),
+        var adapter = new DefaultSubscriptionAdapter(new Subscription(ClientTelemetry.Context),
             (_, _) => throw new InvalidOperationException("boom"));
 
         await Should.NotThrowAsync(() => adapter.DeleteAsync(TestContext.Current.CancellationToken));

tests/Client/ZB.MOM.WW.OtOpcUa.Client.Shared.Tests/OpcUaClientServiceTests.cs

@@ -860,7 +860,6 @@ public class OpcUaClientServiceTests : IDisposable
     [Fact]
     public async Task GetRedundancyInfoAsync_MissingOptionalArrays_ReturnsGracefully()
     {
-        var readCallIndex = 0;
         var session = new FakeSessionAdapter
         {
             ReadResponseFunc = nodeId =>
@@ -1554,7 +1553,7 @@ public class OpcUaClientServiceTests : IDisposable
             {
                 await _service.SubscribeAsync(nodeId);
                 await _service.UnsubscribeAsync(nodeId);
-            }));
+            }, TestContext.Current.CancellationToken));
         }
 
         // No InvalidOperationException from concurrent Dictionary mutation.
@@ -1634,7 +1633,6 @@ public class OpcUaClientServiceTests : IDisposable
         var alarmFakeSub = new FakeSubscriptionAdapter();
 
         // First CreateSubscription call → data subscription; second → alarm subscription.
-        var callIndex = 0;
         var session = new FakeSessionAdapter
         {
             NextSubscription = dataFakeSub