checkpoint(render): preserve pre-overhaul investigation state

src/AcDream.Content/MeshExtractor.cs

@@ -619,7 +619,22 @@ public sealed class MeshExtractor {
             BoundingBox = boundingBox,
             SortCenter = gfxObj?.SortCenter ?? Vector3.Zero,
             DIDDegrade = gfxObj != null && gfxObj.Flags.HasFlag(GfxObjFlags.HasDIDDegrade) ? gfxObj.DIDDegrade : 0,
-            SelectionSphere = new Sphere { Origin = boundingBox.Center, Radius = Vector3.Distance(boundingBox.Max, boundingBox.Min) / 2.0f }
+            // Retail CGfxObj::Serialize @ 0x00534970 stores drawing_sphere as
+            // BSPTREE::GetSphere(drawing_bsp), and RenderDeviceD3D::DrawMesh
+            // @ 0x005A0860 passes that exact sphere to viewconeCheck.  The
+            // vertex-AABB sphere used here previously is a different shape
+            // (notably on long Facility Hub stair sections) and can change a
+            // portal-edge admission decision.  Preserve the authored root
+            // sphere in prepared content; retain the AABB only for malformed
+            // or drawing-BSP-less assets which have no retail sphere to carry.
+            SelectionSphere = gfxObj?.DrawingBSP?.Root?.BoundingSphere
+                ?? new Sphere
+                {
+                    Origin = boundingBox.Center,
+                    Radius = Vector3.Distance(
+                        boundingBox.Max,
+                        boundingBox.Min) / 2.0f,
+                }
         };
     }