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>

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

@@ -61,6 +61,87 @@ public class IndoorCellStencilPipelineTests
         Assert.Equal(new Vector3(1, 1, 0), verts[2]);
     }
 
+    [Fact]
+    public void BuildTriangles_OnlyIncludesProvidedVisibleCells()
+    {
+        // The render path now feeds BuildTriangles from the portal traversal's
+        // visible cells, not every cell in the building. A hidden room's exit
+        // portal must not punch outdoor terrain into the current view.
+        var visibleInnerCell = new LoadedCell
+        {
+            WorldTransform = Matrix4x4.Identity,
+            Portals = new() { new CellPortalInfo(0x0102, 100, 0) },
+            ClipPlanes = new() { default },
+            PortalPolygons = new()
+            {
+                new[]
+                {
+                    new Vector3(0, 0, 0),
+                    new Vector3(1, 0, 0),
+                    new Vector3(1, 1, 0),
+                },
+            },
+        };
+
+        var hiddenExitCell = new LoadedCell
+        {
+            WorldTransform = Matrix4x4.Identity,
+            Portals = new() { new CellPortalInfo(0xFFFF, 101, 0) },
+            ClipPlanes = new() { default },
+            PortalPolygons = new()
+            {
+                new[]
+                {
+                    new Vector3(10, 0, 0),
+                    new Vector3(11, 0, 0),
+                    new Vector3(11, 1, 0),
+                },
+            },
+        };
+
+        var visibleOnly = PortalMeshBuilder.BuildTriangles(new List<LoadedCell> { visibleInnerCell });
+        var allBuildingCells = PortalMeshBuilder.BuildTriangles(new List<LoadedCell> { visibleInnerCell, hiddenExitCell });
+
+        Assert.Empty(visibleOnly);
+        Assert.Equal(3, allBuildingCells.Length);
+        Assert.Equal(new Vector3(10, 0, 0), allBuildingCells[0]);
+    }
+
+    [Fact]
+    public void BuildTriangles_CameraSideFilterSkipsExitPortalsBehindCamera()
+    {
+        var cell = new LoadedCell
+        {
+            WorldTransform = Matrix4x4.Identity,
+            InverseWorldTransform = Matrix4x4.Identity,
+            Portals = new() { new CellPortalInfo(0xFFFF, 100, 0) },
+            ClipPlanes = new()
+            {
+                new PortalClipPlane
+                {
+                    Normal = Vector3.UnitX,
+                    D = 0f,
+                    InsideSide = 0,
+                },
+            },
+            PortalPolygons = new()
+            {
+                new[]
+                {
+                    new Vector3(0, 0, 0),
+                    new Vector3(0, 1, 0),
+                    new Vector3(0, 0, 1),
+                },
+            },
+        };
+
+        var visible = PortalMeshBuilder.BuildTriangles(new List<LoadedCell> { cell }, new Vector3(1, 0, 0));
+        var rejected = PortalMeshBuilder.BuildTriangles(new List<LoadedCell> { cell }, new Vector3(-1, 0, 0));
+
+        Assert.Equal(3, visible.Length);
+        Assert.Empty(rejected);
+    }
+
     [Fact]
     public void BuildTriangles_TriangulatesAsFan()
     {