v0.9.0

Features

• SceneRenderItem::render_as_wireframe: per-item wireframe override independent of the global wireframe_mode setting
• PointCloudItem::gaussian: Gaussian splat falloff (exp(-3d²)) per point cloud; replaces hard circular clip with a soft alpha fade
• Add colourmaps: magma, inferno, turbo, jet, rdbu
• GPU implicit surface rendering
  • GpuImplicitItem, ImplicitPrimitive, ImplicitBlendMode, GpuImplicitOptions
  • Primitive types: sphere, box, plane, capsule; up to 16 per draw call
  • Blend modes: Union, SmoothUnion (per-primitive smooth-min radius), Intersection
  • Submit via SceneFrame::gpu_implicit
  • Showcase 30 extended with a GPU implicit variant as the new default
• GPU marching cubes compute pipeline
  • Z-axis slab chunking: volumes of any size are split internally into slabs sized to fit device.limits().max_buffer_size; no public API change
  • upload_volume_for_mc now returns ViewportResult<VolumeGpuId>; returns Err(ViewportError::McBufferTooLarge) when even a single Z-layer of cells exceeds the device limit, allowing callers to fall back to CPU extraction