refactor(net): converge live session state reset

tests/AcDream.Core.Tests/Items/ExternalContainerStateTests.cs

@@ -68,6 +68,32 @@ public sealed class ExternalContainerStateTests
         Assert.False(state.ApplyViewContents(2u));
     }
 
+    [Fact]
+    public void Reset_RetryRepublishesAndOneObserverCannotStarveAnother()
+    {
+        var state = Open(1u);
+        bool fail = true;
+        int delivered = 0;
+        state.Changed += _ =>
+        {
+            if (fail)
+            {
+                fail = false;
+                throw new InvalidOperationException("transient");
+            }
+        };
+        state.Changed += transition =>
+        {
+            Assert.Equal(ExternalContainerTransitionKind.Reset, transition.Kind);
+            delivered++;
+        };
+
+        Assert.Throws<AggregateException>(() => state.Reset());
+        Assert.Equal(1, delivered);
+        Assert.False(state.Reset());
+        Assert.Equal(2, delivered);
+    }
+
     private static ExternalContainerState Open(uint id)
     {
         var state = new ExternalContainerState();