diag: passage-disabled ceiling (L86); readiness unchanged without passages

Environment-only diagnostic hook disables passage composition (never a world setting).
Cold LOD0-2 / whole @W12 WITHOUT passages: SW 1.12/2.25, FI 2.18/3.34, TN 2.15/3.15, VS 1.12/2.03 s
- the same as with passages (FI 2.16 s). Passages are ~58% of sampled CPU but not the
readiness bottleneck. A lazy exact passage-result cache was +47% slower (24% hit rate, ~700 MB)
and was removed. No world change.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016dhxM43dnWvUu2B5Ph1iG1

Standalone/Core/src/ShapeWorldInternal.h

@@ -31,6 +31,19 @@
 #include <variant>
 #include <vector>
 
+// L86-only ceiling measurement. This removes passage carving/support and the transition-mouth
+// passage fade so timing can measure the best possible passage-representation gain. Never ship
+// or expose this diagnostic as a world setting.
+static bool VF_IsL86PassageCompositionDisabled()
+{
+    static const bool bDisabled = []()
+    {
+        const char* Value = std::getenv("VOXELFORGE_L86_DISABLE_PASSAGE_COMPOSITION");
+        return Value && Value[0] == '1' && Value[1] == '\0';
+    }();
+    return bDisabled;
+}
+
 // Standalone-only world compiler. It compiles the runtime room/tunnel/passages into
 // axis-line intervals, composes rock/cave signs into packed Z-column words, then displaces
 // only the conservative surface band. The copied Unreal generator remains the A/B reference.
@@ -195,19 +208,26 @@ public:
         {
             mayContainResolvedBoundaryBand_=shape.ResolvedBoundaryBandsIntersectSubvoxelRange(
                 minimumSubvoxels_[2],maximumSubvoxels_[2]);
-            mayContainTransitionPassageFade_=shape.ResolvedTransitionPassageFadeIntersectsTileXY(
-                minimumSubvoxels_,maximumSubvoxels_);
-            featureIndices_=shape.BuildPassageFeatureTileList(
-                minimumSubvoxels_,maximumSubvoxels_);
+            const bool disablePassageComposition = VF_IsL86PassageCompositionDisabled();
+            mayContainTransitionPassageFade_ = !disablePassageComposition
+                && shape.ResolvedTransitionPassageFadeIntersectsTileXY(
+                    minimumSubvoxels_, maximumSubvoxels_);
+            if (!disablePassageComposition)
+            {
+                featureIndices_ = shape.BuildPassageFeatureTileList(
+                    minimumSubvoxels_, maximumSubvoxels_);
+            }
             stampIndices_=shape.BuildStampTileList(minimumSubvoxels_,maximumSubvoxels_);
             cavernFeatureIndices_=shape.BuildCavernFeatureTileList(
                 minimumSubvoxels_,maximumSubvoxels_);
-            passageRoutes_.assign(shape.ResolvedLayout?shape.ResolvedLayout->passages.size():0,0);
+            passageRoutes_.assign(shape.ResolvedLayout && !disablePassageComposition
+                ? shape.ResolvedLayout->passages.size() : 0, 0);
             passageColumns_=passageRoutes_;
             passageMouthSupports_=passageRoutes_;
             passageMouthSupportSegments_.resize(passageRoutes_.size());
             passageSegmentRangeCaches_.resize(passageRoutes_.size());
-            if(shape.ResolvedLayout&&!shape.ResolvedLayout->passages.empty())
+            if(!disablePassageComposition&&shape.ResolvedLayout
+                &&!shape.ResolvedLayout->passages.empty())
             {
                 constexpr double Q=static_cast<double>(
                     VoxelForgeCore::WorldAssemblySubvoxelsPerVoxel);
@@ -238,11 +258,14 @@ public:
                         upperMouthSupportPassages_.push_back(passageIndex);
                 }
             }
-            for(const auto& crossing:shape.PassageVoidCrossings)
-                if(crossing.needsColumn
-                    &&crossing.bottomZSubvoxels<=maximumSubvoxels_[2]
-                    &&crossing.topZSubvoxels>=minimumSubvoxels_[2])
-                    columnZOverlap_=true;
+            if(!disablePassageComposition)
+            {
+                for(const auto& crossing:shape.PassageVoidCrossings)
+                    if(crossing.needsColumn
+                        &&crossing.bottomZSubvoxels<=maximumSubvoxels_[2]
+                        &&crossing.topZSubvoxels>=minimumSubvoxels_[2])
+                        columnZOverlap_=true;
+            }
             for(const std::uint32_t featureIndex:featureIndices_)
             {
                 if(featureIndex>=shape.PassageTileFeatures.size())continue;
@@ -2233,7 +2256,7 @@ public:
         // mouth that crosses a wide transition band. Keep that opt-in field whole;
         // its host-rock value already supplies the ceiling and bedrock.
         float boundary=graphDensity;
-        if(!nativeLattice)
+        if(!nativeLattice && !VF_IsL86PassageCompositionDisabled())
         {
             VoxelForgeCore::Linux77Profiler::FScopedPhase l77BandsPhase(
                 VoxelForgeCore::Linux77Profiler::EPhase::Bands);