feat(runtime): atomically replace collision generations

src/AcDream.Runtime/Gameplay/RuntimeLocalPlayerPhysicsPublicationState.cs

@@ -388,6 +388,14 @@ internal sealed class RuntimeLocalPlayerPhysicsPublicationState : IDisposable
             return RuntimeLocalPlayerPhysicsPublicationStatus.RejectedAuthority;
         }
 
+        // Seal the exact SetPosition owner before the irreversible no-fail
+        // suffix. Any internal invariant failure therefore leaves every
+        // canonical body/controller owner untouched.
+        _physics.SetPosition.PrepareDormantLocalActivationOwnership(
+            candidate.Record,
+            candidate.Body,
+            candidate.PreparedActivation.Token.Placement);
+
         // All validation is complete. The remaining stores are callback-free,
         // non-allocating, and cannot fail on this single Runtime update thread.
         // The controller remains RuntimeOwnedDormant; the subsequent world