fix(worker): StaWaitHelper regression tests + full-drain contract notes; consolidate wait P/Invoke

src/ZB.MOM.WW.MxGateway.Worker/Sta/StaMessagePump.cs

@@ -9,10 +9,7 @@ namespace ZB.MOM.WW.MxGateway.Worker.Sta;
 public sealed class StaMessagePump
 {
     private const uint Infinite = 0xFFFFFFFF;
-    private const uint MsgWaitFailed = 0xFFFFFFFF;
-    private const uint MwmoInputAvailable = 0x0004;
     private const uint PmRemove = 0x0001;
-    private const uint QsAllInput = 0x04FF;
 
     /// <summary>Waits for a command wake event or Windows messages, pumping any pending messages.</summary>
     /// <param name="commandWakeEvent">Event to signal when work is available.</param>
@@ -28,14 +25,14 @@ public sealed class StaMessagePump
 
         SafeWaitHandle safeHandle = commandWakeEvent.SafeWaitHandle;
         IntPtr[] handles = [safeHandle.DangerousGetHandle()];
-        uint result = MsgWaitForMultipleObjectsEx(
+        uint result = StaNativeMethods.MsgWaitForMultipleObjectsEx(
             (uint)handles.Length,
             handles,
             timeoutMilliseconds,
-            QsAllInput,
-            MwmoInputAvailable);
+            StaNativeMethods.QsAllInput,
+            StaNativeMethods.MwmoInputAvailable);
 
-        if (result == MsgWaitFailed)
+        if (result == StaNativeMethods.MsgWaitFailed)
         {
             throw new InvalidOperationException(
                 "The worker STA message pump failed while waiting for command work or Windows messages.");
@@ -75,14 +72,6 @@ public sealed class StaMessagePump
             : (uint)Math.Ceiling(timeout.TotalMilliseconds);
     }
 
-    [DllImport("user32.dll", SetLastError = true)]
-    private static extern uint MsgWaitForMultipleObjectsEx(
-        uint count,
-        IntPtr[] handles,
-        uint milliseconds,
-        uint wakeMask,
-        uint flags);
-
     [DllImport("user32.dll", SetLastError = true)]
     private static extern bool PeekMessage(
         out NativeMessage message,