probe: InitializeConsumer required — provider visible after, alarms still absent

InitializeConsumer was the missing call. Adding it before
RegisterConsumer makes the \Galaxy! provider appear in
GetProviders (status 0 -> 100 within 500ms). Without Initialize,
GetProviders returns an empty list even though everything else
returns rc=0 (success).

Probe trace 2026-05-01:

  InitializeConsumer -> 0
  RegisterConsumer -> 0
  GetProviders [after Register] -> count=0 list=[]
  Subscribe('\Galaxy!') -> 0
  GetProviders [after Subscribe] -> count=1 list=[  0 \Galaxy!]
  GetProviders [poll #1] -> count=1 list=[100 \Galaxy!]

Despite the provider being at "100% query complete" for the
entire 60s window, GetStatistics continued to report
total=0 active=0 codes=[7] -- no alarm transitions reached the
consumer even with a System Platform script flipping
TestMachine_001.TestAlarm001 every 10s during the run.

So the consumer chain works end-to-end. What's missing is alarm
traffic from the producer side. The next discriminator is
whether ObjectViewer (or another live consumer) sees the alarm
fire while the script runs.

API-ordering bug fix to apply to PR A.5's AlarmClientConsumer
regardless of how A.2 lands: AlarmClientConsumer.Subscribe
should call InitializeConsumer before RegisterConsumer (currently
omits Initialize entirely, which means the provider chain is
never visible from the worker either). That fix lifts a
fundamental bug independent of the polling-vs-callback question.

Probe changes:

- Added InitializeConsumer call before RegisterConsumer.
- Added LogProviders helper that logs only on change; called
  after Register, after Subscribe, and on every poll. Easier
  to spot when the provider chain transitions from empty to
  populated.
- Restored Skip-gating after run.

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

src/MxGateway.Worker.Tests/AlarmClientWmProbeTests.cs

@@ -231,6 +231,22 @@ public sealed class AlarmClientWmProbeTests : IDisposable
         try
         {
             client = new AlarmClient();
+
+            // Try InitializeConsumer first — separate from RegisterConsumer
+            // per the discovered API surface; previous probe runs skipped
+            // it. Some AVEVA managed-client patterns require Initialize
+            // before Register; others reverse the order. Try Initialize
+            // first; on failure proceed to Register.
+            try
+            {
+                int init = client.InitializeConsumer("AlarmProbe.Tests");
+                Log($"InitializeConsumer -> {init}");
+            }
+            catch (Exception ex)
+            {
+                Log($"InitializeConsumer threw: {ex.GetType().Name}: {ex.Message}");
+            }
+
             int register = client.RegisterConsumer(
                 hWnd: probeWindow.ToInt32(),
                 szProductName: "AlarmProbe",
@@ -239,18 +255,7 @@ public sealed class AlarmClientWmProbeTests : IDisposable
                 bRetainHiddenAlarms: false);
             Log($"RegisterConsumer -> {register}");
 
-            // Discover what providers AVEVA sees before subscribing, so we
-            // can spot a wrong subscription expression up front.
-            try
-            {
-                var providers = new System.Collections.Generic.List<string>();
-                int gp = client.GetProviders(providers);
-                Log($"GetProviders -> rc={gp} count={providers.Count} list=[{string.Join(", ", providers)}]");
-            }
-            catch (Exception ex)
-            {
-                Log($"GetProviders threw: {ex.GetType().Name}: {ex.Message}");
-            }
+            LogProviders(client, "after Register");
 
             int subscribe = client.Subscribe(
                 szSubscription: SubscriptionExpression,
@@ -261,6 +266,8 @@ public sealed class AlarmClientWmProbeTests : IDisposable
                 FilterSpecification: eAlarmFilterState.asNone);
             Log($"Subscribe('{SubscriptionExpression}') -> {subscribe}");
 
+            LogProviders(client, "after Subscribe");
+
             // 3c. Pump for the configured duration. Log every message we see
             //    (filtered light to avoid noise from WM_PAINT / WM_TIMER /
             //    WM_GETICON spam from typical pumps). Poll GetStatistics on
@@ -290,6 +297,7 @@ public sealed class AlarmClientWmProbeTests : IDisposable
                 if (DateTime.UtcNow >= nextPoll)
                 {
                     PollGetStatistics(client, ++pollCount);
+                    LogProviders(client, $"poll #{pollCount}");
                     nextPoll = DateTime.UtcNow + PollInterval;
                 }
                 Thread.Sleep(10);
@@ -316,6 +324,26 @@ public sealed class AlarmClientWmProbeTests : IDisposable
     }
 
     private string lastStatsSummary = string.Empty;
+    private string lastProvidersSummary = string.Empty;
+
+    private void LogProviders(AlarmClient client, string when)
+    {
+        try
+        {
+            var providers = new System.Collections.Generic.List<string>();
+            int rc = client.GetProviders(providers);
+            string summary = $"count={providers.Count} list=[{string.Join(", ", providers)}]";
+            if (summary != lastProvidersSummary)
+            {
+                Log($"GetProviders [{when}] -> rc={rc} {summary} (changed)");
+                lastProvidersSummary = summary;
+            }
+        }
+        catch (Exception ex)
+        {
+            Log($"GetProviders [{when}] threw: {ex.GetType().Name}: {ex.Message}");
+        }
+    }
 
     /// <summary>
     ///     Drive an MxAccess write to <see cref="TriggerTagReference"/> with the