fix(runtime): restore interaction completion ownership

Preserve prepublication local motion completion, require the PartArray enter-world lifecycle port, and balance deferred Use busy ownership across dispatch and cancellation. Reconcile the completed GameWindow connected gates and add regression coverage.

Co-authored-by: Codex <codex@openai.com>

src/AcDream.App/World/LiveEntityPartArrayEnterWorldPort.cs

@@ -0,0 +1,22 @@
+namespace AcDream.App.World;
+
+/// <summary>
+/// Strongly typed retail PartArray world-entry boundary.
+/// </summary>
+/// <remarks>
+/// <c>CPhysicsObj::set_hidden @ 0x00514C60</c> invokes
+/// <c>CPartArray::HandleEnterWorld @ 0x00517D70</c> on both Hidden edges.
+/// This dedicated port prevents that mandatory lifecycle callback from being
+/// confused with neighboring <see cref="Action{T}"/> presentation callbacks.
+/// </remarks>
+public sealed class LiveEntityPartArrayEnterWorldPort
+{
+    private readonly Action<uint> _handleEnterWorld;
+
+    public LiveEntityPartArrayEnterWorldPort(Action<uint> handleEnterWorld) =>
+        _handleEnterWorld = handleEnterWorld
+            ?? throw new ArgumentNullException(nameof(handleEnterWorld));
+
+    public void HandleEnterWorld(uint localEntityId) =>
+        _handleEnterWorld(localEntityId);
+}