fix(render): FW4 slice 3 - the outside-stage predicate reads the walk flood

The cathedral falls persisted through the slice-2 seal fix; the probe
already held the tell: the same two emitter entities (f4243/f4285) draw
phase=pre on good frames and phase=post on bad ones. They are
interior-parented, so DynamicDrawsInOutsideStage takes the indoor arm,
whose first gate is flood membership - and that still read the OLD
apparatus flood, which drops cells at the #456 seam band. On those
frames the falls fell to the post-clear last pass and splatted across
the cleared depth (terrain and water alike).

Both predicate call sites (the frame product's BuildOutsideDynamicRoutes
via BuildAndBorrow's input, and the renderer's own outside-stage
classification) now receive the walk's VisitedCells on walk frames -
root flood plus look-in floods, all of whose objects retail draws inside
LScape::draw, pre-clear. drawableCells keeps its other roles. Also adds
the probe-gated [walk-dyn] per-entity classification dump (parent cell,
outside/cone verdicts) so a surviving repro pins the failing gate
directly.

Hermetic 6,762/0, Walk lane 213/1.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/AcDream.App/Rendering/RetailPViewRenderer.cs

@@ -465,6 +465,18 @@ public sealed class RetailPViewRenderer
         _candidateObserver?.BeginPViewFrame();
         try
         {
+            // FW4 slice 3: the outside-stage predicate's flood-membership set
+            // is THE WALK'S visited cells on walk frames (root flood +
+            // look-in floods — retail draws all of their objects inside
+            // LScape::draw, pre-clear). The old apparatus's drawableCells
+            // misses cells at the #456 seam band, dropping interior-parented
+            // outdoor emitters (the cathedral falls weenies) to the
+            // post-clear last pass, where the cleared depth lets them splat
+            // across terrain and water. drawableCells keeps its other roles
+            // (prepare filter, frame result) unchanged.
+            HashSet<uint> outsideStageFlood =
+                walkActive ? walkDriver!.VisitedCells : drawableCells;
+
             if (_sceneFrameProduct is not null)
             {
                 frameView = _sceneFrameProduct.BuildAndBorrow(
@@ -472,7 +484,7 @@ public sealed class RetailPViewRenderer
                     clipAssembly,
                     viewcone,
                     _lookInFrames,
-                    drawableCells,
+                    outsideStageFlood,
                     ctx.Cells,
                     ctx.AnimatedEntityIds,
                     ctx.RootCell.IsOutdoorNode);
@@ -544,7 +556,11 @@ public sealed class RetailPViewRenderer
                 foreach (var e in partition.Dynamics)
                 {
                     EntitySphere(e, out var c, out float r);
-                    if (DynamicDrawsInOutsideStage(e.ParentCellId, c, r, drawableCells, ctx.Cells))
+                    // FW4 slice 3: same walk-flood membership set as the
+                    // frame product's BuildOutsideDynamicRoutes — the two
+                    // predicate call sites must agree or routed and drawn
+                    // stages diverge.
+                    if (DynamicDrawsInOutsideStage(e.ParentCellId, c, r, outsideStageFlood, ctx.Cells))
                         _outsideStageDynamics.Add(e);
                 }
             }

src/AcDream.App/Rendering/Scene/RenderScenePViewFrameProduct.cs

@@ -1141,6 +1141,10 @@ internal sealed class RenderScenePViewFrameBuilder
     private readonly Dictionary<RenderProjectionId, int>
         _dynamicPositions = [];
     private int _dynamicCount;
+
+    // ACDREAM_PROBE_WALK_ROOT companion (throwaway): rate limiter for the
+    // [walk-dyn] outside-stage classification dump.
+    private uint _probeDynFrameCounter;
     private int _dirtyCount;
     private RenderSceneGeneration _indexGeneration;
     private ulong _indexRevision;
@@ -1320,6 +1324,9 @@ internal sealed class RenderScenePViewFrameBuilder
             return;
 
         int sliceCount = input.ClipAssembly.OutsideViewSlices.Length;
+        bool probeDynamics =
+            AcDream.Core.Rendering.RenderingDiagnostics.ProbeWalkRootEnabled
+            && ++_probeDynFrameCounter % 120 == 0;
         for (int sliceIndex = 0; sliceIndex < sliceCount; sliceIndex++)
         {
             int count = 0;
@@ -1328,19 +1335,23 @@ internal sealed class RenderScenePViewFrameBuilder
             {
                 RenderProjectionRecord record = _dynamics[i];
                 Sphere(in record, out Vector3 center, out float radius);
-                if (!RetailPViewRenderer.DynamicDrawsInOutsideStage(
+                bool outside = RetailPViewRenderer.DynamicDrawsInOutsideStage(
                     ParentCell(in record),
                     center,
                     radius,
                     input.DrawableCells,
-                        input.Cells)
+                    input.Cells);
-                    || !input.Viewcone.SphereVisibleInOutsideSlice(
+                bool cone = input.Viewcone.SphereVisibleInOutsideSlice(
-                        sliceIndex,
+                    sliceIndex, in center, radius);
-                        in center,
+                if (probeDynamics)
-                        radius))
                 {
-                    continue;
+                    Console.WriteLine(
+                        $"[walk-dyn] slice={sliceIndex} id={record.Source.LocalEntityId:x} "
+                        + $"parent={ParentCell(in record)?.ToString("x8") ?? "null"} "
+                        + $"r={radius:F1} outside={(outside ? 1 : 0)} cone={(cone ? 1 : 0)}");
                 }
+                if (!outside || !cone)
+                    continue;
 
                 _survivors[count++] = record;
                 writer.AddDynamic(in record);