wip: L175 fix tile seams - passage-affected X8 lanes use the composed path (v241, RED)

Seam audit: 0 mismatches over 16 seeds (99,269 pairs, 121.6M shared samples),
injected control detected. Step-2 overlap/turn failures remain. Mainline has the
same dispatch structure (not changed).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011g9Ez42ZNqQGjigc4FWDih

Standalone/Core/src/ShapeWorldInternal.h

@@ -228,6 +228,17 @@ public:
         FSurfaceWorldFieldAdapter,FFloatingIslandFieldAdapter,
         FCavesFieldAdapter,FLegacyGeneratorFieldAdapter>;
 
+    inline static thread_local std::uint32_t PassageX8OutsideProofDepth=0;
+    class FScopedPassageX8OutsideProof
+    {
+    public:
+        FScopedPassageX8OutsideProof(){++PassageX8OutsideProofDepth;}
+        ~FScopedPassageX8OutsideProof(){--PassageX8OutsideProofDepth;}
+        FScopedPassageX8OutsideProof(const FScopedPassageX8OutsideProof&)=delete;
+        FScopedPassageX8OutsideProof& operator=(const FScopedPassageX8OutsideProof&)=delete;
+        static bool IsActive() noexcept{return PassageX8OutsideProofDepth!=0;}
+    };
+
     struct FBoundStratumField
     {
         enum class EKind : uint8 { Legacy, SurfaceWorld, FloatingIslands, Caves };
@@ -1298,6 +1309,14 @@ public:
         {
             const std::size_t passageIndex=passageTileScopeMatches
                 ?(*routePassageIndices)[routeOffset]:routeOffset;
+            // A passage can be in this tile's list because a different route segment
+            // overlaps the tile. Check the sample before its landing chamber is composed.
+            if(passageTileScopeMatches
+                &&!passageTileQueries->routeFeatureMayAffect(passageIndex,qx,qy,qz))
+            {
+                passageTileQueries->recordFeatureBoundSkip();
+                continue;
+            }
             const auto& passage=ResolvedLayout->passages[passageIndex];
             if(passage.controlPoints.size()<2)continue;
             const bool surfaceDepartureLanding=queryStratum&&queryStratum->Resolved
@@ -3710,7 +3729,50 @@ public:
                 static_cast<uint64>(Count));
             FScopedRoute l77Route(ERoute::SharedSource);
             FScopedPhase l77Phase(EPhase::BaseField);
-            SharedDensitySource->DensityAtLatticeX8(XStart,XStep,Y,Z,Count,OutDensity);
+            const int32 ActiveCount=std::clamp(Count,0,8);
+            const auto* TileQueries=FScopedPassageTileQueries::CurrentFor(*this);
+            const auto& Source=*SharedDensitySource;
+            const bool bOldFastEligible=Source.EditBrushes.empty()
+                &&Y>=Source.Min[1]&&Y<=Source.Max[1]
+                &&Z>=Source.Min[2]&&Z<=Source.Max[2]
+                &&XStart>=Source.Min[0]
+                &&XStart+static_cast<int64>(ActiveCount-1)*XStep<=Source.Max[0];
+            const bool bHasResolvedPassages=ResolvedLayout
+                &&!ResolvedLayout->passages.empty();
+            std::array<bool,8> LaneMayBeAffected{};
+            const auto mayBeAffected=[&](int32 Lane)
+            {
+                if(!TileQueries)return bHasResolvedPassages;
+                const double Q=static_cast<double>(
+                    VoxelForgeCore::WorldAssemblySubvoxelsPerVoxel);
+                const double X=static_cast<double>(XStart+Lane*XStep)*Q;
+                const double QY=static_cast<double>(Y)*Q;
+                const double QZ=static_cast<double>(Z)*Q;
+                for(const std::size_t passageIndex:TileQueries->routePassageIndices())
+                    if(TileQueries->routeFeatureMayAffect(passageIndex,X,QY,QZ))
+                        return true;
+                return false;
+            };
+            for(int32 Lane=0;Lane<ActiveCount;++Lane)
+                LaneMayBeAffected[static_cast<std::size_t>(Lane)]=mayBeAffected(Lane);
+            // The shared X8 source contains only the base field. Route-bound lanes
+            // use the composed scalar path; only unaffected runs delegate to X8.
+            for(int32 Lane=0;Lane<ActiveCount;)
+            {
+                if(LaneMayBeAffected[static_cast<std::size_t>(Lane)])
+                {
+                    OutDensity[Lane]=DensityAtLattice(XStart+Lane*XStep,Y,Z);
+                    ++Lane;
+                    continue;
+                }
+                const int32 RunStart=Lane;
+                while(Lane<ActiveCount
+                    &&!LaneMayBeAffected[static_cast<std::size_t>(Lane)])++Lane;
+                FScopedPassageX8OutsideProof outsideProof;
+                SharedDensitySource->DensityAtLatticeX8(
+                    XStart+RunStart*XStep,XStep,Y,Z,Lane-RunStart,
+                    OutDensity+RunStart);
+            }
             return;
         }
         Count=std::clamp(Count,0,8);
@@ -3782,6 +3844,10 @@ public:
             &&Z>=Min[2]&&Z<=Max[2]
             &&XStart>=Min[0]
             &&XStart+static_cast<int64>(Count-1)*XStep<=Max[0];
+        const bool bOldFastEligible=bFast;
+        const auto* TileQueries=FScopedPassageTileQueries::CurrentFor(*this);
+        if(!TileQueries&&ResolvedLayout&&!ResolvedLayout->passages.empty()
+            &&!FScopedPassageX8OutsideProof::IsActive())bFast=false;
         if(!bFast)
         {
             for(int32 Lane=0;Lane<Count;++Lane)
@@ -3802,6 +3868,24 @@ public:
         constexpr float ProxyBandEdge=DetailSupremum+0.125f;
         for(int32 Lane=0;Lane<Count;++Lane)
         {
+            bool bPassageMayAffectLane=false;
+            if(TileQueries)
+            {
+                const double Q=static_cast<double>(
+                    VoxelForgeCore::WorldAssemblySubvoxelsPerVoxel);
+                const double SampleX=static_cast<double>(XStart+Lane*XStep)*Q;
+                const double SampleY=static_cast<double>(Y)*Q;
+                const double SampleZ=static_cast<double>(Z)*Q;
+                for(const std::size_t passageIndex:TileQueries->routePassageIndices())
+                    if(TileQueries->routeFeatureMayAffect(passageIndex,
+                        SampleX,SampleY,SampleZ))
+                    {bPassageMayAffectLane=true;break;}
+            }
+            if(bPassageMayAffectLane)
+            {
+                OutDensity[Lane]=DensityAtLattice(XStart+Lane*XStep,Y,Z);
+                continue;
+            }
             const size_t Column=ColumnStart+static_cast<size_t>(Lane*XStep);
             const size_t Word=Column*WordsPerZ+WordOffset;
             const bool bRock=(RockWords[Word]&Mask)!=0;