feat(render): Phase A8 — indoor visibility + streaming fixes batch

Lands the working A8 indoor-rendering and streaming fixes accumulated this
session. User has verified these visually to some degree (e.g. lifestone /
translucent meshes confirmed fine under the FrontFace flip; bridge / wall /
collision regressions confirmed fixed after travel); not every path has been
exhaustively gated. The cellar-flap defect remains OPEN and will be solved
the retail-faithful way via a dedicated brainstorm (see handoff docs).

Rendering core (reviewed, high confidence):
- EnvCellRenderer SSBO stride fix: upload packed Matrix4x4[] (64B) instead of
  the 80B CPU InstanceData struct the shader never expected — fixes the
  transform/texture "explosion" for any draw with >1 instance (cells that
  dedupe to a shared cellGeomId). Real root cause.
- WB-style global FrontFace(CW) + per-batch CullMode carried through the MDI
  layout (GroupKey + BuildIndirectArrays + DrawIndirectRange split into
  same-cull runs with absolute uDrawIDOffset per run).
- EntitySet partitioning (IndoorPass / OutdoorScenery / LiveDynamic) +
  WorldEntity.BuildingShellAnchorCellId so building shells scope to their
  dat-derived building cell instead of rendering everywhere.
- RenderOutsideInAcdream (look into buildings from outside) +
  CollectVisiblePortalBuildings frustum cull of portal bounds.
- Sky-when-inside-building + per-cell audit probe + GL-state probe.

Streaming / perf (test-covered; not independently code-reviewed this session):
- Near/far priority queues so near work wins over far; PromoteToNear carries
  full landblock + mesh data; LandblockEntriesWithoutAnimatedIndex avoids
  rebuilding the animated-lookup dict in the hot draw path. Fixes the
  bridge-not-appearing / missing-walls / broken-collision-after-travel
  regressions and improves post-transition FPS.

Tooling + docs:
- tools/A8CellAudit: offline dat cell/portal/building dumper (portals +
  buildings modes) — reproduces the cellar-flap investigation with no launch.
- docs/research cellar-flap root-cause + option-2 handoff (the didInsideStencil
  double-duty finding + the WB-recursive design decision + brainstorm prompt),
  entity-taxonomy, replan, issue-78 visibility investigation.

Diagnostics retained on purpose: ACDREAM_A8_DIAG_* gates, portal_stencil.vert
provisional pos.w clamp, and the probe families are kept (env-var gated, zero
cost when off) because the pending option-2 cellar-flap brainstorm needs them.
Strip in the option-2 ship commit.

Indoor branch stays behind ACDREAM_A8_INDOOR_BRANCH=1 (default off = pre-A8
visual). Build green; App tests + Core (streaming/dispatcher/loader) tests pass.

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

src/AcDream.Core/World/LandblockLoader.cs

@@ -1,5 +1,6 @@
 using DatReaderWriter;
 using DatReaderWriter.DBObjs;
+using DatReaderWriter.Types;
 
 namespace AcDream.Core.World;
 
@@ -83,6 +84,7 @@ public static class LandblockLoader
                 Rotation = building.Frame.Orientation,
                 MeshRefs = Array.Empty<MeshRef>(),
                 IsBuildingShell = true,  // Phase A8: tag at source array boundary
+                BuildingShellAnchorCellId = FirstBuildingAnchorCellId(building, landblockId),
             };
             buildingEntity.RefreshAabb(); // A.5 T18: populate cached AABB at construction
             result.Add(buildingEntity);
@@ -96,4 +98,20 @@ public static class LandblockLoader
         var type = id & TypeMask;
         return type == GfxObjMask || type == SetupMask;
     }
+
+    private static uint? FirstBuildingAnchorCellId(BuildingInfo building, uint landblockId)
+    {
+        if (landblockId == 0)
+            return null;
+
+        uint lbPrefix = landblockId & 0xFFFF0000u;
+        foreach (var portal in building.Portals)
+        {
+            if (portal.OtherCellId == 0xFFFF)
+                continue;
+            return lbPrefix | (uint)portal.OtherCellId;
+        }
+
+        return null;
+    }
 }

src/AcDream.Core/World/WorldEntity.cs

@@ -56,13 +56,24 @@ public sealed class WorldEntity
     ///
     /// <para>
     /// Read at draw time by <c>WbDrawDispatcher</c>'s <c>IndoorPass</c>
-    /// partition so building shells render unconditionally when the camera
-    /// is inside their building (they ARE the indoor walls), not stencil-gated
-    /// as outdoor scenery would be.
+    /// partition so building shells can render when the camera is inside their
+    /// own building (they ARE the indoor walls), not stencil-gated as outdoor
+    /// scenery would be.
     /// </para>
     /// </summary>
     public bool IsBuildingShell { get; init; }
 
+    /// <summary>
+    /// Dat-derived EnvCell anchor for a building shell. Building shells are
+    /// top-level landblock stabs, so they do not have a real ParentCellId, but
+    /// the LandBlockInfo.Buildings[] portal list names cells owned by the same
+    /// building. The indoor renderer uses this anchor only for draw scoping:
+    /// a shell renders in IndoorPass when its anchor belongs to the camera
+    /// building's EnvCell set. Collision still treats the shell as an outdoor
+    /// stab unless ParentCellId is explicitly set.
+    /// </summary>
+    public uint? BuildingShellAnchorCellId { get; init; }
+
     /// <summary>
     /// Uniform scale applied to this entity's mesh by the scenery pipeline.
     /// For scenery objects this is spawn.Scale (typically 0.8–1.3). For stabs