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/final/round_w1.stdout.log

@@ -0,0 +1,6 @@
+Standalone clip override: exported radius=6 (112 m cube) -> radius=1 (32 m LOD0 cube), voxel size=25 cm.
+[StreamBenchmarkConfig] clip_radius=1 lod0_cube=32m voxel=25cm fullres_levels=2 max_level_filter=0 workers=1 full_detail_tiles=64 desired_tiles=64 variant=round-detailed
+[StreamFullDetail] wall=5.513s generated=64/64 resident_tiles_cpu_only=1 density_hash=0x73721f3f6bc15756
+[StreamFullClipmap] wall=5.513s generated=64/64 worker_sum=5.511s tiles=64 density_hash=0x73721f3f6bc15756
+[StreamCacheUse] hits=0 requested=64
+[StreamLevel] lod=0 tiles=64 samples=2.744M worker_sum=5.511s vertices=84259 indices=479682 density_hash=0x73721f3f6bc15756