fix(tests): stabilize three flaky tests under parallel full-solution load

#1 EventPumpBoundedChannelTests.Tags_metrics_with_client_name_for_multi_driver_hosts:
Replace fixed Task.Delay(100) with a poll-until-condition loop (5 s
timeout, 25 ms poll) so the test waits until the galaxy.events.received
measurement for galaxy.client=Driver-X actually lands in the listener.
Also adds lock(captured) in the MeterListener callback and at all reads,
since Counter.Add() fires the callback on the RunAsync background thread.

#2 VirtualTagEngineTests.Upstream_change_triggers_cascade_through_two_levels:
After waiting for B=15.0, also await WaitForConditionAsync for C=30.0
before asserting C. The cascade runs B then C sequentially under the
_evalGate semaphore; the prior code could read C while its evaluation
had not yet acquired the gate.

#3 ThreeUserInteropMatrixTests.Admin_Resolves_All_Five_Groups_From_LDAP:
Wrap the AuthenticateAsync call in a 15 s linked CancellationTokenSource
with one retry so transient GLAuth latency spikes under parallel test
load do not cause a CancellationToken expiry before the LDAP bind/search
complete.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Tests/Runtime/EventPumpBoundedChannelTests.cs

@@ -87,9 +87,11 @@ public sealed class EventPumpBoundedChannelTests
         {
             if (instr.Meter.Name == EventPump.MeterName) l.EnableMeasurementEvents(instr);
         };
+        // The callback fires on the thread that calls Counter.Add() — that is the
+        // RunAsync background Task. Use lock(captured) everywhere to avoid torn reads.
         listener.SetMeasurementEventCallback<long>((instr, _, tags, _) =>
         {
-            captured.Add((instr.Name, tags.ToArray()));
+            lock (captured) { captured.Add((instr.Name, tags.ToArray())); }
         });
         listener.Start();
 
@@ -101,17 +103,40 @@ public sealed class EventPumpBoundedChannelTests
         {
             pump.Start();
             await subscriber.EmitAsync(7, 42.0);
-            await Task.Delay(100);
-            listener.RecordObservableInstruments();
+
+            // Poll until at least one galaxy.events.received measurement tagged
+            // galaxy.client=Driver-X lands in the listener, rather than using a
+            // fixed delay that races under parallel test load on a busy box.
+            var deadline = DateTime.UtcNow.AddSeconds(5);
+            bool found = false;
+            while (DateTime.UtcNow < deadline)
+            {
+                listener.RecordObservableInstruments();
+                bool hasMatch;
+                lock (captured)
+                {
+                    hasMatch = captured.Any(c =>
+                        c.Instrument == "galaxy.events.received" &&
+                        c.Tags.Any(t => t.Key == "galaxy.client" &&
+                            string.Equals((string?)t.Value, "Driver-X", StringComparison.Ordinal)));
+                }
+                if (hasMatch) { found = true; break; }
+                await Task.Delay(25);
+            }
+            _ = found; // assertion happens below after dispose
         }
 
         // The static Meter is shared across all EventPump instances in the test
         // assembly; xUnit may run other pump tests in parallel and their
         // measurements land on the same listener. Filter to our pump's tag value.
-        var ours = captured
-            .Where(c => c.Tags.Any(t => t.Key == "galaxy.client"
-                && string.Equals((string?)t.Value, "Driver-X", StringComparison.Ordinal)))
-            .ToList();
+        List<(string Instrument, KeyValuePair<string, object?>[] Tags)> ours;
+        lock (captured)
+        {
+            ours = captured
+                .Where(c => c.Tags.Any(t => t.Key == "galaxy.client"
+                    && string.Equals((string?)t.Value, "Driver-X", StringComparison.Ordinal)))
+                .ToList();
+        }
 
         ours.ShouldNotBeEmpty(
             "at least one measurement from this test's pump must carry galaxy.client=Driver-X");