fix(streaming): preserve portal destination ownership

Detach old-world spatial ownership atomically, prioritize destination retirement dependencies, and reveal the viewport at the retail transition edge. Give private paperdoll views independent mesh ownership and retain dormant ACE entities so portal revisits preserve server objects without extending active GPU lifetimes.

tests/AcDream.App.Tests/Streaming/StreamingCompletionQueueTests.cs

@@ -110,6 +110,39 @@ public sealed class StreamingCompletionQueueTests
         Assert.Equal(0, snapshot.OldestAgeMilliseconds);
     }
 
+    [Fact]
+    public void PriorityCeilingLeavesNearAndFarWorkRetained()
+    {
+        var queue = new StreamingCompletionQueue();
+        StreamingQueuedCompletion near = Completion(
+            new LandblockStreamResult.Failed(20, "near"),
+            StreamingCompletionPriority.Near,
+            sequence: 1);
+        StreamingQueuedCompletion unload = Completion(
+            new LandblockStreamResult.Unloaded(21),
+            StreamingCompletionPriority.Unload,
+            sequence: 2);
+        queue.Enqueue(near);
+        queue.Enqueue(unload);
+
+        Assert.True(queue.TryPeekNext(
+            static _ => false,
+            out StreamingQueuedCompletion? selected,
+            StreamingCompletionPriority.Unload));
+        Assert.Equal(unload.Sequence, selected?.Sequence);
+        queue.RemoveHead(unload);
+
+        Assert.False(queue.TryPeekNext(
+            static _ => false,
+            out selected,
+            StreamingCompletionPriority.Unload));
+        Assert.Equal(1, queue.Count);
+        Assert.True(queue.TryPeekNext(
+            static _ => false,
+            out selected));
+        Assert.Equal(near.Sequence, selected?.Sequence);
+    }
+
     [Fact]
     public void ExactReferenceRemovalDoesNotConflateEqualRecords()
     {