Improve gateway reliability and dashboard docs

src/MxGateway.Worker/MxAccess/MxAccessSession.cs

@@ -79,7 +79,14 @@ public sealed class MxAccessSession : IDisposable
         }
         catch (Exception exception)
         {
-            eventSink.Detach();
+            try
+            {
+                eventSink.Detach();
+            }
+            catch
+            {
+                // Preserve the creation failure while still releasing the COM object below.
+            }
 
             if (mxAccessComObject is not null && Marshal.IsComObject(mxAccessComObject))
             {
@@ -535,13 +542,15 @@ public sealed class MxAccessSession : IDisposable
 
     private void DisposeCore(ICollection<MxAccessShutdownFailure>? failures)
     {
+        Exception? detachException = null;
         try
         {
             eventSink.Detach();
         }
-        catch (Exception exception) when (failures is not null)
+        catch (Exception exception)
         {
-            failures.Add(new MxAccessShutdownFailure(
+            detachException = exception;
+            failures?.Add(new MxAccessShutdownFailure(
                 "DetachEvents",
                 serverHandle: null,
                 itemHandle: null,
@@ -565,6 +574,10 @@ public sealed class MxAccessSession : IDisposable
         }
 
         disposed = true;
+        if (detachException is not null && failures is null)
+        {
+            throw detachException;
+        }
     }
 
     private void ThrowIfDisposed()