standalone: 64 m full-detail override, detailed round tunnels, optional mesh cache -- generation itself NOT faster

ClipRadius override 3 (64 m at 25 cm). Uncached full detail 20.3 s on 8 workers (512 tiles at
~51 ms serial each should be ~3-4 s: the in-stream inefficiency is unsolved); full clipmap 170.6 s.
The 1 s / 5 s targets were met only from an on-disk mesh cache (.vfmesh, not committed) of
already-generated tiles: a revisit speed-up, not generation speed. Round tunnels gained
deterministic multi-scale wall relief and lost the larger mouth wedges (1.54% of lattice signs
changed, mean 0.20 m). Hashes stable across runs and 1 vs 6 workers.

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

Standalone/Research/VoxelSpeedRound/preliminary/round_detail_probe16.stdout.log

@@ -0,0 +1,3 @@
+[BenchmarkConfig] tile_cache_window=1 fused_min_lod=3 room_graph_cache_slots=1 command='--benchmark-level=0 --benchmark-count=16 --density-hash --round-tunnels --camera=-11.75,-123.25,-19.85,90,0'
+[TileBenchmark] LOD=0 generated=16 samples=0.69M worker_sum=1.380s avg=86.246ms p50=80.643ms p95=97.313ms vertices=13698 indices=78207 profiling=off
+[TileDensityHash] LOD=0 tiles=16 hash=0x2cf5287b33cbead6