feat(render): Phase A8 Wave 3 — wire EnvCellRenderer into landblock streaming

Six surgical edits to GameWindow.cs (+1 MeshManager accessor on WbMeshAdapter):

1. Field declarations (line 166-167): _envCellRenderer + _envCellFrustum.
2. Ctor init (line 1775-1778): construct WbFrustum + EnvCellRenderer,
   Initialize with the existing _meshShader (loaded from mesh_modern.vert/frag).
3. BuildInteriorEntitiesForStreaming (line 5444): _envCellRenderer.RegisterCell(...)
   replaces the cell-as-WorldEntity creation block. staticObjects is empty —
   cell stabs continue as WorldEntity records via the dispatcher's IndoorPass.
4. ApplyLoadedTerrainLocked (line 5885): _envCellRenderer.FinalizeLandblock(...)
   immediately after _buildingRegistries[lb.LandblockId] = ... — atomically
   commits the landblock's per-cell instance store.
5. RemoveLandblock callbacks (lines 1861 + 8955): mirror the existing
   _buildingRegistries.Remove(id) sites so EnvCellRenderer's storage clears
   in lockstep.
6. Dispose (line 10595): _envCellRenderer?.Dispose() after _wbDrawDispatcher.

Plan revision (vs original plan.md Task 6): we keep the static-object stab
WorldEntity hydration (lines 5440-5489) instead of deleting it — stabs need
WorldEntity records for interaction (clicking) and physics. EnvCellRenderer
receives empty staticObjects so it only renders cell geometry; stab rendering
continues unchanged through the dispatcher.

Build green. 23/23 EnvCellRenderer + WbFrustum + EnvCellSceneryInstance
tests pass. App.Tests baseline holds (82/82). Pre-existing Core.Tests
static-leak flakiness (8-19 failures, documented baseline) unrelated.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/AcDream.App/Rendering/GameWindow.cs

@@ -158,6 +158,14 @@ public sealed class GameWindow : IDisposable
     private readonly System.Collections.Generic.Dictionary<uint, AcDream.App.Rendering.Wb.BuildingRegistry>
         _buildingRegistries = new();
 
+    // Phase A8 (2026-05-28): WB EnvCellRenderManager port. Cells render
+    // through this dedicated pipeline now, NOT through WbDrawDispatcher.
+    // The dispatcher's IndoorPass still walks cell-static stabs (WorldEntity
+    // records with real GfxObj MeshRefs); only the cell GEOMETRY (walls /
+    // floors / ceilings) flows through here.
+    private AcDream.App.Rendering.Wb.EnvCellRenderer? _envCellRenderer;
+    private AcDream.App.Rendering.Wb.WbFrustum? _envCellFrustum;
+
     /// <summary>
     /// Phase 6.4: per-entity animation playback state for entities whose
     /// MotionTable resolved to a real cycle. The render loop ticks each
@@ -1760,6 +1768,14 @@ public sealed class GameWindow : IDisposable
                 _classificationCache);
             // A.5 T22.5: apply A2C gate from quality preset.
             _wbDrawDispatcher.AlphaToCoverage = _resolvedQuality.AlphaToCoverage;
+
+            // Phase A8: EnvCellRenderer init. Shares _meshShader (mesh_modern.{vert,frag})
+            // with the dispatcher — both consume the same global mesh buffer (VAO/IBO)
+            // from ObjectMeshManager.GlobalBuffer.
+            _envCellFrustum = new AcDream.App.Rendering.Wb.WbFrustum();
+            _envCellRenderer = new AcDream.App.Rendering.Wb.EnvCellRenderer(
+                _gl, _wbMeshAdapter!.MeshManager!, _envCellFrustum);
+            _envCellRenderer.Initialize(_meshShader!);
         }
 
         // Phase G.1 sky renderer — its own shader (sky.vert / sky.frag)
@@ -1842,6 +1858,7 @@ public sealed class GameWindow : IDisposable
                 _physicsEngine.RemoveLandblock(id);
                 _cellVisibility.RemoveLandblock((id >> 16) & 0xFFFFu);
                 _buildingRegistries.Remove(id);  // Phase A8
+                _envCellRenderer?.RemoveLandblock(id);  // Phase A8
             });
         // A.5 T22.5: apply max-completions from resolved quality.
         _streamingController.MaxCompletionsPerFrame = _resolvedQuality.MaxCompletionsPerFrame;
@@ -5398,6 +5415,13 @@ public sealed class GameWindow : IDisposable
                 if (environment is not null
                     && environment.Cells.TryGetValue(envCell.CellStructure, out cellStruct))
                 {
+                    // Phase A8 (2026-05-28): cells render through EnvCellRenderer, NOT as
+                    // WorldEntities with fake MeshRefs. The CellMesh.Build call stays for
+                    // _pendingCellMeshes (still populated for any consumer) and the physics
+                    // data cache (CacheCellStruct uses cellStruct directly, not the sub-meshes).
+                    // Static objects inside the cell continue to flow through the dispatcher
+                    // as WorldEntity records below — they have real GfxObj MeshRefs that work
+                    // fine; EnvCellRenderer.RegisterCell receives an empty staticObjects list.
                     var cellSubMeshes = AcDream.Core.Meshing.CellMesh.Build(envCell, cellStruct, _dats);
                     if (cellSubMeshes.Count > 0)
                     {
@@ -5414,23 +5438,23 @@ public sealed class GameWindow : IDisposable
                             System.Numerics.Matrix4x4.CreateFromQuaternion(envCell.Position.Orientation) *
                             System.Numerics.Matrix4x4.CreateTranslation(physicsCellOrigin);
 
-                        var cellMeshRef = new AcDream.Core.World.MeshRef(envCellId, cellTransform);
+                        // Phase A8: register the cell with EnvCellRenderer for rendering.
+                        // staticObjects is empty — cell stabs continue as separate WorldEntity
+                        // records via the dispatcher (see lines below for the unchanged stab path).
+                        _envCellRenderer?.RegisterCell(
+                            landblockId:       landblockId,
+                            envCellId:         envCellId,
+                            envCell:           envCell,
+                            cellStruct:        cellStruct,
+                            cellTransform:     cellTransform,
+                            cellWorldPosition: cellOrigin,
+                            cellRotation:      envCell.Position.Orientation,
+                            staticObjects:     System.Array.Empty<(uint, System.Numerics.Vector3, System.Numerics.Quaternion, bool, System.Numerics.Matrix4x4)>());
 
-                        var cellEntity = new AcDream.Core.World.WorldEntity
-                        {
-                            Id = interiorIdBase + localCounter++,
-                            SourceGfxObjOrSetupId = envCellId,
-                            Position = System.Numerics.Vector3.Zero,
-                            Rotation = System.Numerics.Quaternion.Identity,
-                            MeshRefs = new[] { cellMeshRef },
-                            ParentCellId = envCellId,
-                        };
-                        result.Add(cellEntity);
-
-                        // Step 4: build LoadedCell for portal visibility.
+                        // Step 4: build LoadedCell for portal visibility (UNCHANGED from pre-A8).
                         BuildLoadedCell(envCellId, envCell, cellStruct, cellOrigin, cellTransform);
 
-                        // Cache CellStruct physics BSP for indoor collision.
+                        // Cache CellStruct physics BSP for indoor collision (UNCHANGED).
                         _physicsDataCache.CacheCellStruct(envCellId, envCell, cellStruct, physicsCellTransform);
                     }
                 }
@@ -5854,6 +5878,11 @@ public sealed class GameWindow : IDisposable
                     AcDream.App.Rendering.Wb.BuildingLoader.Build(
                         lbInfo, lb.LandblockId, drainedCells);
             }
+
+            // Phase A8: finalize EnvCellRenderer's per-landblock instance store.
+            // Atomically swaps PendingInstances -> committed, computes TotalEnvCellBounds,
+            // populates StaticPartGroups/BuildingPartGroups via PopulateRecursive.
+            _envCellRenderer?.FinalizeLandblock(lb.LandblockId);
         }
 
         // N.5: WbMeshAdapter.Tick() handles GPU upload for all GfxObj meshes via
@@ -8923,6 +8952,7 @@ public sealed class GameWindow : IDisposable
                     _physicsEngine.RemoveLandblock(id);
                     _cellVisibility.RemoveLandblock((id >> 16) & 0xFFFFu);
                     _buildingRegistries.Remove(id);  // Phase A8
+                    _envCellRenderer?.RemoveLandblock(id);  // Phase A8
                 });
             _streamingController.MaxCompletionsPerFrame = newResolved.MaxCompletionsPerFrame;
 
@@ -10562,6 +10592,7 @@ public sealed class GameWindow : IDisposable
         _liveSession = null;
         _audioEngine?.Dispose();  // Phase E.2: stop all voices, close AL context
         _wbDrawDispatcher?.Dispose();
+        _envCellRenderer?.Dispose();  // Phase A8
         _skyRenderer?.Dispose();      // depends on sampler cache; dispose first
         _samplerCache?.Dispose();
         _textureCache?.Dispose();

src/AcDream.App/Rendering/Wb/WbMeshAdapter.cs

@@ -120,6 +120,13 @@ public sealed class WbMeshAdapter : IDisposable, IWbMeshAdapter
     /// </summary>
     public AcSurfaceMetadataTable MetadataTable => _metadataTable;
 
+    /// <summary>
+    /// Phase A8 (2026-05-28): exposes the underlying <see cref="ObjectMeshManager"/>
+    /// so <c>EnvCellRenderer</c> can share the same global mesh buffer (VAO/VBO/IBO).
+    /// Returns null when the adapter is uninitialized.
+    /// </summary>
+    public ObjectMeshManager? MeshManager => _meshManager;
+
     /// <summary>
     /// Returns the WB render data for <paramref name="id"/>, or null if not
     /// yet uploaded or if this adapter is uninitialized. Increments WB's