feat(ui): centralize retail selection state

tests/AcDream.App.Tests/UI/ItemInteractionControllerTests.cs

@@ -77,6 +77,10 @@ public sealed class ItemInteractionControllerTests
 
         Assert.True(h.Controller.IsTargetModeActive);
         Assert.True(h.Controller.IsPendingSource(0x50000A01u));
+        Assert.Equal(InteractionModeKind.UseItemOnTarget,
+            h.Controller.InteractionState.Current.Kind);
+        Assert.Equal(0x50000A01u,
+            h.Controller.InteractionState.Current.SourceObjectId);
         Assert.Empty(h.UseWithTarget);
     }