refactor(runtime): close simulation ownership

Move remote-motion construction, CreateObject vector initialization, final simulation-component retirement, and the combined J5 ownership ledger into Runtime. Delete App compatibility views and moved-state reconstruction while preserving the existing graphical projection and retail update order.

src/AcDream.Core/Physics/PhysicsEngine.cs

@@ -168,6 +168,27 @@ public sealed class PhysicsEngine
         DataCache?.CellGraph.RemoveLandblock(landblockId);
     }
 
+    /// <summary>
+    /// Releases every collision landblock and retained shadow registration
+    /// owned by this engine. Runtime calls this only at terminal disposal;
+    /// ordinary streaming still uses the typed per-landblock retirement path.
+    /// </summary>
+    public void Clear()
+    {
+        if (_landblocks.Count != 0)
+        {
+            var landblocks = new uint[_landblocks.Count];
+            _landblocks.Keys.CopyTo(landblocks, 0);
+            foreach (uint landblockId in landblocks)
+                RemoveLandblock(landblockId);
+        }
+
+        // Dynamic live registrations can remain intentionally suspended with
+        // no cell rows after their last landblock retires. Terminal engine
+        // ownership must retire those logical registrations as well.
+        ShadowObjects.Clear();
+    }
+
     /// <summary>
     /// Retire a Near landblock's indoor-cell and static-object collision layer
     /// while preserving its terrain surface and world offset for Far-tier use.

src/AcDream.Core/Physics/ShadowObjectRegistry.cs

@@ -795,6 +795,21 @@ public sealed class ShadowObjectRegistry
     /// <summary>Suspended logical registrations awaiting spatial re-entry.</summary>
     public int SuspendedRegistrationCount => _suspendedEntities.Count;
 
+    /// <summary>
+    /// Retires the complete logical registry at terminal physics-engine
+    /// disposal, including suspended live registrations that own no cell row.
+    /// </summary>
+    public void Clear()
+    {
+        _cells.Clear();
+        _entityToCells.Clear();
+        _suspendedEntities.Clear();
+        _withdrawnPrefixesByOwner.Clear();
+        _entityShapes.Clear();
+        _entityReg.Clear();
+        _fallback = null;
+    }
+
     /// <summary>
     /// Debug: enumerate every registered ShadowEntry (deduplicated across cells).
     /// Single-shape entities return one entry per shape; multi-part entities