feat(rendering): compare scene-built PView candidates

Build a same-frame candidate product from incremental render-scene indices and compare its exact PView routes against the accepted current path without changing the production draw source.

src/AcDream.App/Rendering/RetailPViewRenderer.cs

@@ -15,6 +15,8 @@ public sealed class RetailPViewRenderer
 {
     private readonly InteriorEntityPartition.IObserver? _partitionObserver;
     private readonly ICurrentRenderPViewObserver? _candidateObserver;
+    private readonly RenderScenePViewFrameProductController?
+        _sceneFrameProduct;
     private readonly PortalVisibilityFrame _mainPortalFrameScratch = new();
     private readonly ClipFrameAssembly _clipAssemblyScratch = new();
     private readonly ViewconeCuller _viewconeScratch = new();
@@ -71,10 +73,19 @@ public sealed class RetailPViewRenderer
     }
 
     internal RetailPViewRenderer(
-        InteriorEntityPartition.IObserver? partitionObserver)
+        InteriorEntityPartition.IObserver? partitionObserver,
+        RenderScenePViewFrameProductController? sceneFrameProduct = null)
     {
+        if (sceneFrameProduct is not null
+            && partitionObserver is not ICurrentRenderPViewObserver)
+        {
+            throw new ArgumentException(
+                "The scene frame-product referee requires the current PView observer.",
+                nameof(partitionObserver));
+        }
         _partitionObserver = partitionObserver;
         _candidateObserver = partitionObserver as ICurrentRenderPViewObserver;
+        _sceneFrameProduct = sceneFrameProduct;
     }
 
     // T2 (BR-4): retail has NO distance constant on the flood-admission chain
@@ -239,6 +250,14 @@ public sealed class RetailPViewRenderer
             DrawDynamicsLast(ctx, passes, partition, viewcone, ctx.RootCell.IsOutdoorNode);
 
             _candidateObserver?.CompletePViewFrame();
+            _sceneFrameProduct?.BuildAndCompare(
+                pvFrame,
+                clipAssembly,
+                viewcone,
+                _lookInFrames,
+                drawableCells,
+                ctx.Cells,
+                ctx.RootCell.IsOutdoorNode);
             return result;
         }
         catch