refactor(net): converge live session state reset

tests/AcDream.Core.Tests/Selection/SelectionStateTests.cs

@@ -24,6 +24,33 @@ public sealed class SelectionStateTests
         Assert.False(state.SelectPrevious());
     }
 
+    [Fact]
+    public void Reset_RetryRepublishesAndOneObserverCannotStarveAnother()
+    {
+        var state = new SelectionState();
+        state.Select(0x50000001u, SelectionChangeSource.World);
+        bool fail = true;
+        int delivered = 0;
+        state.Changed += _ =>
+        {
+            if (fail)
+            {
+                fail = false;
+                throw new InvalidOperationException("transient");
+            }
+        };
+        state.Changed += transition =>
+        {
+            Assert.Equal(SelectionChangeReason.SessionReset, transition.Reason);
+            delivered++;
+        };
+
+        Assert.Throws<AggregateException>(() => state.Reset());
+        Assert.Equal(1, delivered);
+        Assert.False(state.Reset());
+        Assert.Equal(2, delivered);
+    }
+
     [Fact]
     public void Select_CommitsOneTransitionAndTracksPreviousLikeRetail()
     {