wip(assembler): round S5 -- streaming gates + trace; coarse-first order kept opt-in (no win)

Walkable/enclosed/refined gates defined; JSONL trace joins request, worker start,
build/apply and discards. Coarse-first + dynamic near reserve behind
voxel.StreamingCoarseFirst / voxel.StreamingDynamicNearReserve (default 0 =
S4 order): matched runs showed no walkability or full-view win and slower
LOD0/1 refinement. Instruments settled: 3.1 s standalone reproduced (16.7 s was
another generation route); black early captures were clear-only frames.
Hashes equal S4; Core-off, M2, SurfaceWorld/FloatingIslands BuildHost pass.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MmSoF64BbRFmk9C3p1VsBJ

Source/VoxelForge/Public/VoxelWorld.h

@@ -139,6 +139,11 @@ struct FChunkResult
     uint64 GenerationEndCycles = 0;
     uint64 ApplyStartCycles = 0;
     EVoxelTileWorkPriority WorkPriority = EVoxelTileWorkPriority::Horizon;
+    // Ordinals make admitted order and actual worker start order auditable across MPSC results.
+    // Les numeros d'ordre rendent auditables l'admission et le demarrage des workers via MPSC.
+    uint64 RequestOrdinal = 0;
+    uint64 GenerationOrdinal = 0;
+    bool bResidentAtRequest = false;
     // Step-1-only tag captured on the game thread for the pawn's bounded support cohort.
     bool bStep1SupportCohort = false;
     int32 ClassifyVerdict = -1; double ClassifySeconds = 0.0; double MeshSeconds = 0.0; double StreamSeconds = 0.0; int32 NumTriangles = 0; int32 NumCeilingTriangles = 0; int32 NumSkirtTriangles = 0;
@@ -1179,6 +1184,9 @@ public:
     uint32 DesiredEpoch = 0;               // increments whenever DesiredStamped is rebuilt
     int32 ObsoleteTileAbortCount = 0;      // cumulative per-world moving-session cancellation count
     float PeakObservedPawnSpeedCmPerSecond = 0.0f;
+    int32 EffectiveNearTaskReserve = -1;
+    uint64 NextStreamingRequestOrdinal = 0;
+    std::atomic<uint64> NextStreamingGenerationOrdinal{0};
 
     struct FReadyTransitionVisibilitySample
     {
@@ -1257,6 +1265,11 @@ public:
     bool bHeadlessStreamingTestExitOnSteady = false;
     bool bHeadlessStreamingTestExitRequested = false;
     bool bStartupTraceThroughCrossing = false;
+    bool bStartupTraceUntilEndPlay = false;
+    bool bHasLastWalkableGateSample = false;
+    bool bLastWalkableGateReady = false;
+    FIntVector LastWalkableGateCenter = FIntVector::ZeroValue;
+    double LastStreamingTraceSampleSeconds = 0.0;
     bool bHeadlessStreamingTestCenterOverride = false;
     FVector HeadlessStreamingTestCenterVoxel = FVector::ZeroVector;
     int32 HeadlessStreamingTestMoveAttempts = 0;