fix(app): Phase 9.2 — enable back-face cull in translucent pass

The user reported the lifestone crystal (AlphaBlend part 3 of the
4-part 0x020002EE setup) rendered with one side consistently missing
— looked like "a box with one side missing, you can see into it"
while the whole thing rotated.

Isolated via experiment: routing the crystal through the opaque pass
(no blending, depth write on) produced a whole solid shape. Routing
it through the Phase 9.1 translucent pass (blending on, depth write
off) produced the hole. Mesh build was eliminated as the cause.

Root cause: our translucent pass matched WorldBuilder's state
(SrcAlpha/OneMinusSrcAlpha, DepthMask(false)) but NOT its culling
state. WorldBuilder enables GL_CULL_FACE with per-batch CullMode
(references/WorldBuilder/Chorizite.OpenGLSDLBackend/Lib/
BaseObjectRenderManager.cs:361-365). Without face culling, the 58
triangles of the closed crystal shell drew in dict-iteration order;
back faces that happened to draw AFTER front faces composited over
them because depth-write-off meant nothing recorded depth within the
translucent set. One face of the crystal ended up permanently
overwritten by its own backside.

Fix: in pass 2 (translucent) enable GL_CULL_FACE with GL_BACK and
CCW front-face winding. Our mesh builder emits pos-side triangles as
(0, i, i+1), which is CCW in standard OpenGL conventions, so GL_BACK
correctly drops the inward-facing side. Back-face culling is disabled
again after pass 2 so subsequent renderers (terrain etc.) see the
default state.

Known limitation: neg-side polys on translucent surfaces — which my
pos/neg mesh-build fix would have emitted with reversed winding —
now get culled in the translucent pass. AC rarely uses double-sided
polygons on translucent surfaces so this is acceptable, and the
opaque pass still renders them correctly. A future Phase 9.3 can
track CullMode per sub-mesh and draw double-sided translucents with
GL_NONE if it turns out to matter.

Also strips the Portal/Lifestone [DIAG] spawn dump that served as
one-shot evidence gathering during the investigation.

194 tests green.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/AcDream.App/Rendering/StaticMeshRenderer.cs

@@ -135,6 +135,30 @@ public sealed unsafe class StaticMeshRenderer : IDisposable
         _gl.Enable(EnableCap.Blend);
         _gl.DepthMask(false);
 
+        // Phase 9.2: enable back-face culling for the translucent pass so
+        // closed-shell translucents (lifestone crystal, glow gems, any
+        // convex blended mesh) don't draw their back faces over their
+        // front faces in arbitrary iteration order. Without this, the
+        // 58 triangles of the lifestone crystal composited with an
+        // "inside-out" look where the user saw through one face into
+        // the hollow interior. With back-face culling on, back faces are
+        // dropped at rasterization time, front faces composite as-is,
+        // and depth ordering within the front-facing subset is a
+        // non-issue for closed convex-ish shells. Matches WorldBuilder's
+        // per-batch CullMode handling in
+        // references/WorldBuilder/Chorizite.OpenGLSDLBackend/Lib/
+        // BaseObjectRenderManager.cs:361-365.
+        //
+        // Our fan triangulation emits pos-side polygons as
+        // (0, i, i+1) which is CCW in standard OpenGL conventions, so
+        // GL_BACK + CCW front is the correct state. Neg-side polygons
+        // (if any) use reversed winding and get culled here — that's a
+        // known limitation and matches the opaque-pass behavior since
+        // neg-side polys are virtually never translucent in AC content.
+        _gl.Enable(EnableCap.CullFace);
+        _gl.CullFace(TriangleFace.Back);
+        _gl.FrontFace(FrontFaceDirection.Ccw);
+
         foreach (var entity in entityList)
         {
             if (entity.MeshRefs.Count == 0)
@@ -191,6 +215,7 @@ public sealed unsafe class StaticMeshRenderer : IDisposable
         // Restore default GL state for subsequent renderers (terrain etc.).
         _gl.DepthMask(true);
         _gl.Disable(EnableCap.Blend);
+        _gl.Disable(EnableCap.CullFace);
 
         _gl.BindVertexArray(0);
     }