Fix direct voxel fast path stabilization

[agustin-littlehat]

Summary

• Use an 8px direct voxel primitive on mobile-class documents while preserving CSS-space geometry, avoiding the 1x1 <b> quad gaps seen on mobile.
• Move the crack bench normalize bundle off the deleted website/src/debug/meshDomNormalize file and onto the current optimizeMeshPolygons pipeline.
• Add the GPU-default Chromium bench helper plus voxel/non-voxel trace and hypothesis probes used to keep measuring renderer/compositor paths.
• Remove the temporary gallery CSS-keyframes auto-rotate experiment and lil-gui mode toggle before merge.

Verification

• node bench/build.mjs
• pnpm test
• pnpm build