wip(assembler): round S11 -- bounded spawn apply budget: in-game full set 7.1 s -> 6.0 s

Startup apply mode on by default (12 meshes / 14 ms per frame, ends when the
initial set and walkable ring are ready, 30 s cap); normal play keeps the
authored budget. Backlog peak 252 -> 10, LOD8 apply wait 1.1 s -> 4 ms.
Ring 0.49 s, LOD0 1.40 s, 40 m/s ring 75/75. Remaining floor: frame-paced
admission (~8.3 submits/frame, 8 running workers max). No geometry change.
Report: Standalone/Research/WorldAssemblerM3/Round15.

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

Source/VoxelForge/Public/VoxelWorld.h

@@ -1225,6 +1225,8 @@ public:
     bool bSampleStacksStarted = false;
     bool bStartupApplyBoostStarted = false;
     bool bStartupApplyBoostEnded = false;
+    // Trace the resolved startup budget once per world. / Tracer une fois le budget de demarrage resolu par monde.
+    bool bStartupApplyConfigTraced = false;
     uint64 LastApplyFrameCycles = 0;
     float StartupTraceSpeedCmPerSecond = 0.0f;
     TArray<FVoxelTileKey> DesiredSorted;   // critical floor prefix, then true-pawn distance-first