feat(overhaul): port S5 particle cell visibility

Publish the exact completed walk landscape set as the typed retained particle-view product. Apply retail CLandCell membership versus constant-true non-null CEnvCell eligibility while preserving the x87 distance and AP-116 behavior.

Delete the null-root terrain visibility reconstruction and the dead drawable-cell point-light feedback chain. Retire AP-117, correct AP-85 and AD-21, and keep directional shadows, building degrade, AP-232, probes, RHI, shaders, and DAT outside this chunk.

Automated return: Release 0 warnings/0 errors; Core VFX 111/111; App particle/frame/renderer/terrain 146/146; warmed production allocation 1/1 at 0 B. First official hermetic artifact s5-c1-hermetic-20260904 is preserved at 16759/16760 with only the stale 162-row assertion; after the bounded 161 correction, exact pin 1/1 and fresh s5-c1-hermetic-corrected-20260904 16760/16760. InstalledDat 385 pass, 10 documented failures, 1 documented skip, no new identity.

Mutation 1: making EnvCell eligibility set-dependent first failed ParticleSystemTests.cs:553 Assert.True, expected true actual false. Mutation 2: making outdoor eligibility constant true first failed ParticleSystemTests.cs:559 Assert.False, expected false actual true.

Mutation 3: feeding the diagnostic union first failed WorldSceneRendererTests.cs:279 HashSet equality, expected [16842755], actual [16843008, 16842755]. Mutation 4: restoring CollectVisibleCells first failed TerrainParticleCellVisibilityTests.cs:37 and named TerrainModernRenderer.cs.

Mutation 5: restoring ObserveDrawableCells first failed TerrainParticleCellVisibilityTests.cs:37 and named WorldRenderFrameBuilder.cs. Mutation 6: changing the inclusive boundary from <= to < first failed ParticleSystemTests.cs:519 Assert.True, expected true actual false.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

tests/AcDream.App.Tests/Rendering/TerrainParticleCellVisibilityTests.cs

@@ -1,58 +1,42 @@
-using System.Numerics;
-using AcDream.App.Rendering;
+using AcDream.App.Tests.Rendering.Walk;
 
 namespace AcDream.App.Tests.Rendering;
 
 /// <summary>
-/// S3 landing hygiene (H2): <see cref="TerrainModernRenderer.CollectVisibleCells"/>
-/// is frustum-only now — its clip-plane-list and NDC-AABB scissor
-/// parameters and the CPU/GPU clip-region equivalence check they fed had
-/// exactly one production caller (<see cref="TerrainModernRenderer.Draw"/>),
-/// and that caller never actually passed either (grep). The doorway-clip/scissor
-/// rejection cases this file used to pin (<c>RejectsCellsOutsideDoorwayClipPlanes</c>,
-/// <c>RejectsCellsOutsideDoorwayScissorAabb</c>, <c>UnionsCellsFromEveryLandscapeSlice</c>)
-/// pinned a mechanism nothing in production ever fed — deleted with the
-/// parameters. What remains still pins the one thing this method's callers
-/// actually rely on: it publishes the visible terrain cell set per landblock,
-/// respecting an explicit frustum when one is given.
+/// Campaign OVERHAUL S5-c1: the null-root terrain path remains a safety draw,
+/// but it may not reconstruct or publish a competing cell-visibility answer.
+/// The same architecture pin protects the deleted point-light feedback seam.
 /// </summary>
 public sealed class TerrainParticleCellVisibilityTests
 {
     [Fact]
-    public void CollectVisibleCells_PublishesLandscapeCellsWithoutEntitySurvivors()
+    public void ProductionRetainsNoReconstructedVisibilityOrLightFeedbackSymbols()
     {
-        var cells = new HashSet<uint>();
+        string sourceRoot = Path.Combine(WalkOracleTraceRepoRoot.Find(), "src");
+        string[] production = Directory.GetFiles(
+            sourceRoot,
+            "*.cs",
+            SearchOption.AllDirectories);
+        string[] forbidden =
+        [
+            "CollectVisibleCells",
+            "TerrainVisibleCellIds",
+            "ObserveDrawableCells",
+            "ClearDrawableCells",
+        ];
 
-        TerrainModernRenderer.CollectVisibleCells(
-            cells,
-            0xA9B4FFFFu,
-            Vector3.Zero,
-            zMin: 0f,
-            zMax: 20f,
-            frustum: null);
-
-        Assert.Equal(64, cells.Count);
-        Assert.Contains(0xA9B40001u, cells);
-        Assert.Contains(0xA9B40040u, cells);
-    }
-
-    [Fact]
-    public void CollectVisibleCells_ForceDrawnParentStillUsesCellFrustum()
-    {
-        var cells = new HashSet<uint>();
-        FrustumPlanes frustum = FrustumPlanes.FromViewProjection(Matrix4x4.Identity);
-
-        // The parent landblock may have entered TerrainModernRenderer's draw
-        // list through neverCullLandblockId. The cell collector deliberately
-        // receives no such bypass and still rejects its off-frustum cells.
-        TerrainModernRenderer.CollectVisibleCells(
-            cells,
-            0xA9B4FFFFu,
-            new Vector3(100f, 100f, 100f),
-            zMin: 100f,
-            zMax: 120f,
-            frustum);
-
-        Assert.Empty(cells);
+        foreach (string symbol in forbidden)
+        {
+            string[] owners = production
+                .Where(path => File.ReadAllText(path).Contains(
+                    symbol,
+                    StringComparison.Ordinal))
+                .Select(path => Path.GetRelativePath(sourceRoot, path))
+                .OrderBy(path => path, StringComparer.Ordinal)
+                .ToArray();
+            Assert.True(
+                owners.Length == 0,
+                $"Production symbol {symbol} remains in: {string.Join(", ", owners)}");
+        }
     }
 }