wip(L5, side branch): Linux offscreen captures + sampled far-LOD gate + no-op octave cutoff

Not for assembler/world: no octave qualifies under the cutoff's supremum criterion (world
unchanged), and the build is +4.6% slower than L4 with the flag off (reviewer interleaved W12).
Keeps the working EGL/GLES capture path and a gate whose metric is vertical height error, which
overstates screen error on steep slopes; its "exact far meshes exceed 1 px / 126 px pop" claims are
unconfirmed. See Linux5/REPORT.md "Orchestrator review".

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01ED33VnqepD4YY6gDAAA832

Standalone/Source/StreamingWorld.h

@@ -646,6 +646,18 @@ public:
     int32 GetWorkerCount()const{return WorkerCount;}
     uint64 GetCacheHits()const{return CacheHitCount.load(std::memory_order_relaxed);}
 
+    void SetVisualDetailCutoffBudgets(const std::array<std::int64_t,9>& Budgets,bool Apply)
+    {VisualDetailBudgetSubvoxels=Budgets;bEnableVisualDetailCutoff=true;bApplyVisualDetailCutoff=Apply;}
+    void SetVisualDetailProfilingEnabled(bool Enabled)
+    {bProfileVisualDetailOctaves=Enabled;}
+    FStandaloneCpuTile GenerateDiagnostic(const FVoxelTileKey& Key,
+        std::uint32_t GlobalOctaveDrop=0,std::uint32_t CellStride=1,
+        bool ForceExactVisualDetail=false)
+    {
+        FStandaloneTileJob Job;Job.Key=Key;Job.StartedAt=FClock::now();Job.QueuedAt=Job.StartedAt;
+        return Generate(Job,GlobalOctaveDrop,CellStride,0,ForceExactVisualDetail);
+    }
+
 private:
     FStandaloneStreamingUpdate UpdateDesiredSet(FStandaloneDesiredTileSet NewDesired,
         const std::vector<FVoxelTileKey>& ResidentKeys,uint64 CrossingIndex)
@@ -761,12 +773,15 @@ private:
         Wake.notify_all();
         return Stats;
     }
-    FStandaloneCpuTile Generate(const FStandaloneTileJob& Job)
+    FStandaloneCpuTile Generate(const FStandaloneTileJob& Job,
+        std::uint32_t DiagnosticGlobalOctaveDrop=0,std::uint32_t DiagnosticCellStride=1,
+        std::int64_t DiagnosticVisualBudgetSubvoxels=0,
+        bool ForceExactVisualDetail=false)
     {
         const auto StartTime=Job.StartedAt;
         FStandaloneCpuTile Out;Out.Key=Job.Key;Out.RequestedCrossing=Job.RequestedCrossing;
         Out.QueuedAt=Job.QueuedAt;Out.StartedAt=Job.StartedAt;
-        if(MeshCache)
+        if(MeshCache&&!ForceExactVisualDetail)
         {
             if(const FStandaloneCpuTile* Cached=MeshCache->Find(Job.Key))
             {
@@ -805,6 +820,21 @@ private:
             Options.skipMaterialGroups=bSkipMaterialGroups;Options.skipUv=bSkipUV;Options.skipColors=bSkipColors;
             Options.captureColumnCoordinates=bCaptureColumnCoordinates;
             Options.lod8HorizonInteriorStepVoxels=Lod8HorizonInteriorStepVoxels;
+            Options.visualDetailPixelBudgetSubvoxels=DiagnosticVisualBudgetSubvoxels;
+            if(DiagnosticVisualBudgetSubvoxels==0&&bEnableVisualDetailCutoff
+                &&Level>=3&&Level<static_cast<int32>(VisualDetailBudgetSubvoxels.size()))
+                Options.visualDetailPixelBudgetSubvoxels=
+                    VisualDetailBudgetSubvoxels[static_cast<std::size_t>(Level)];
+            Options.visualDetailSampleStepVoxels=FMath::Max(1,Extent/Cells);
+            Options.profileVisualDetailOctaves=bProfileVisualDetailOctaves&&!ForceExactVisualDetail;
+            Options.visualDetailCutoffEnabled=bApplyVisualDetailCutoff
+                &&!ForceExactVisualDetail&&Level>=3
+                &&Options.visualDetailPixelBudgetSubvoxels>0;
+            Options.visualDetailContractVersion=Options.visualDetailCutoffEnabled
+                ?VoxelForgeCore::CurrentVisualDetailCutoffContractVersion:0;
+            Options.diagnosticGlobalOctaveDrop=DiagnosticGlobalOctaveDrop;
+            Options.diagnosticColumnInterpolationStride=
+                std::max<std::uint32_t>(1,DiagnosticCellStride);
             std::string Error;
             auto Result=CoreWorld->generateTile(
                 {{Job.Key.Coord.X,Job.Key.Coord.Y,Job.Key.Coord.Z},Job.Key.Level},Options,Error);
@@ -977,6 +1007,10 @@ private:
     bool bSkipColors=false;
     bool bCaptureColumnCoordinates=false;
     int32 Lod8HorizonInteriorStepVoxels=0;
+    std::array<std::int64_t,9> VisualDetailBudgetSubvoxels{};
+    bool bEnableVisualDetailCutoff=false;
+    bool bApplyVisualDetailCutoff=false;
+    bool bProfileVisualDetailOctaves=false;
     std::atomic<uint64> CacheHitCount{0};
     mutable std::mutex Mutex;
     std::condition_variable Wake;