test(opcua-client): replace fixed delays in the ConditionRefresh wire test with ordering barriers (lmxopcua#764)

The 1500 ms pre-control and 500 ms trailing sleeps are gone. ConditionRefresh
completes server-side before SubscribeAlarmsAsync returns, so refresh events
queue ahead of the control Acknowledge; a trailing message-change barrier event
is projected and awaited (bounded 10 s poll) so any stray event must arrive
before it. The assertion is now the exact sequence [Acknowledge, Unspecified],
no weaker than before.

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

tests/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer.IntegrationTests/OpcUaClientDriverWireTests.cs

@@ -310,19 +310,27 @@ public sealed class OpcUaClientDriverWireTests
         var before = Seen().Length;
         await drv.UnsubscribeAlarmsAsync(first, ct);
         await drv.SubscribeAlarmsAsync([AlarmRef], ct);
-        await Task.Delay(1500, ct); // let the second refresh's events land before the control transition
+        // No sleep: ConditionRefresh has completed server-side when SubscribeAlarmsAsync returns, so its events
+        // are already queued on the subscription AHEAD of anything projected below. A re-delivery would
+        // therefore surface before the control events and be caught by the exact-sequence assertion.
 
         // Positive control: an upstream acknowledge arrives as exactly one Acknowledge, after which nothing else.
         rig.Project(native: true, new AlarmConditionSnapshot(Active: true, Acknowledged: true, Confirmed: true,
             Enabled: true, AlarmShelvingKind.Unshelved, 800, "already hot"));
         await RecordedEvents.WaitUntilAsync(() => Seen().Any(e => e.Kind == AlarmTransitionKind.Acknowledge));
-        await Task.Delay(500, ct);
+        // Trailing barrier instead of a quiet period: a further, distinguishable upstream change (new message) is
+        // projected after the Acknowledge and awaited. Events reach the driver in queue order, so anything stray
+        // that was going to follow the Acknowledge must arrive before this marker and is caught below.
+        rig.Project(native: true, new AlarmConditionSnapshot(Active: true, Acknowledged: true, Confirmed: true,
+            Enabled: true, AlarmShelvingKind.Unshelved, 800, "barrier"));
+        await RecordedEvents.WaitUntilAsync(() => Seen().Any(e => e.Message == "barrier"));
         // #728: record each event's full shape on failure, not only its Kind — the extra Unspecified that failed CI
         // could be a changed message/severity, a non-condition event or a quality-only annotation, and the Kind alone
         // cannot tell them apart.
         var after = Seen().Skip(before).ToArray();
-        after.Select(e => e.Kind).ShouldBe([AlarmTransitionKind.Acknowledge],
-            "the second refresh re-delivered an unchanged state and must have emitted nothing; events after the " +
+        after.Select(e => e.Kind).ShouldBe([AlarmTransitionKind.Acknowledge, AlarmTransitionKind.Unspecified],
+            "the second refresh re-delivered an unchanged state and must have emitted nothing (only the Acknowledge " +
+            "and the trailing barrier's message change are expected); events after the " +
             "resubscribe: " + string.Join(" | ", after.Select(Describe)));
     }