feat(app): observe canonical placement receipts

src/AcDream.Runtime/Physics/RuntimePlacementProjectionSubscription.cs

@@ -34,11 +34,25 @@ public sealed class RuntimePlacementProjectionSubscription
     public RuntimePlacementProjectionSubscription(
         GameRuntime runtime,
         IRuntimePlacementProjectionSink sink)
+        : this(runtime, sink, retryPendingOnSubscribe: true)
+    {
+    }
+
+    /// <summary>
+    /// Subscribes before optionally draining the pending FIFO. A session route
+    /// which must publish its own disposal/retry ownership first passes
+    /// <c>false</c>, stores those owners, then calls <see cref="RetryPending"/>.
+    /// </summary>
+    public RuntimePlacementProjectionSubscription(
+        GameRuntime runtime,
+        IRuntimePlacementProjectionSink sink,
+        bool retryPendingOnSubscribe)
         : this(
             runtime?.Placements
                 ?? throw new ArgumentNullException(nameof(runtime)),
             () => runtime.Generation,
-            sink)
+            sink,
+            retryPendingOnSubscribe)
     {
     }
 
@@ -46,13 +60,27 @@ public sealed class RuntimePlacementProjectionSubscription
         RuntimePlacementProjectionChannel channel,
         Func<RuntimeGenerationToken> generation,
         IRuntimePlacementProjectionSink sink)
+        : this(
+            channel,
+            generation,
+            sink,
+            retryPendingOnSubscribe: true)
+    {
+    }
+
+    internal RuntimePlacementProjectionSubscription(
+        RuntimePlacementProjectionChannel channel,
+        Func<RuntimeGenerationToken> generation,
+        IRuntimePlacementProjectionSink sink,
+        bool retryPendingOnSubscribe)
     {
         _channel = channel ?? throw new ArgumentNullException(nameof(channel));
         _generation = generation
             ?? throw new ArgumentNullException(nameof(generation));
         _sink = sink ?? throw new ArgumentNullException(nameof(sink));
         _subscription = _channel.Subscribe(this);
-        _ = RetryPending();
+        if (retryPendingOnSubscribe)
+            _ = RetryPending();
     }
 
     public bool HasAppliedReceiptAwaitingAcknowledgement =>