v0.3.0

MagicaVoxel .vox interop, and the CPU renderer is now the default to dodge a
Windows GPU-init hang.

Added

• MagicaVoxel .vox import and export (File ▸ Open .vox / Export .vox, and a
  .vox path argument). Import uses the dot_vox parser (handles real-world
  files) and takes the first model; export writes a single model. The height
  axis is flipped between MagicaVoxel's z-up and demiurg's z-down so models stay
  upright, and colours map through a 256-entry palette. .vox has no pivot, so
  import centres it.

Fixed

• The 0.2.0 white-window fix wasn't enough: on some Windows GPUs/drivers wgpu
  device creation itself hangs (before the first frame), which a synchronous
  call can't be timed out of. The CPU renderer is now the default (reliable
  everywhere); the GPU backend is opt-in via --gpu or ROXLAP_GPU=1 (--cpu /
  ROXLAP_GPU=0 force CPU).