captures: readable player-view captures with a coverage gate (L69); R36 native-generator survey

- Capture exports now cover a 90-degree player frustum (radius 3, LOD 0-8, overlap patches);
  a 17x9 ray coverage probe aborts before rendering if tiles are missing (truncated-mesh
  control: 480 uncovered samples, rejected). Clear colour is sky blue, so un-meshed space can't
  pass as dark rock. 16 views of the owner's four-strate plan.
- Explore commandlet: finite XYZ spawn override for traces (Source/, Linux-compiled).
- In-engine four-strate trace NOT obtained: the engine-generated plan fails passage validation
  at a solid centerline voxel (~(-43,-34.5,-448.5) m) while the headless owner_world.json
  plan passes. Engine and headless plans diverge.
- R36 (read-only): order TN -> VS -> FI for native migration; native FI is reachable from the
  adapter but not selected in the owner run, cause unknown.

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

Standalone/Source/StreamBenchmarkPipeline.h

@@ -1872,7 +1872,7 @@ namespace StandaloneStreamBenchmark
         bool bExactMidpointDensityMemo=false,
         bool bActiveLaneBatching=false,int32 ProofBlockCells=8,
         bool bParallelSignEdgeRepair=false,bool bAuditNativeLattice=false,
-        bool bLatticeOrphanControl=false)
+        bool bLatticeOrphanControl=false,bool bCaptureSkipWalkability=false)
     {
         using Clock=std::chrono::steady_clock;
         FStandaloneOwnerWorld& World=*OwnerWorld;
@@ -2029,6 +2029,9 @@ namespace StandaloneStreamBenchmark
         ShapeRequest.detail=DetailVariant;ShapeRequest.includeFarWorld=bIncludeFarWorld;
         ShapeRequest.roundTunnels=bRoundTunnels;
         ShapeRequest.enhancedTunnelWalls=bEnhancedTunnelWalls;
+        ShapeRequest.validatePassageRoutes=!bCaptureSkipWalkability;
+        if(bCaptureSkipWalkability)
+            std::printf("[CaptureWalkabilityGate] validation=deferred geometry_input=unchanged mode=mesh-export\n");
         FStandaloneStreamingGenerator Streamer(World,WorkerCount,bHashDensity,nullptr,MaxLevel,
             bSkipUvAndColors,bSkipMaterialGroups,bSkipUV,bSkipColors,&Shape,bProfileColumnOverlap,
             FarHorizonLOD8InteriorStepVoxels,bUseSharedColumnCache);