Function marching_cubes_gpu 

pub fn marching_cubes_gpu(
    ctx: &GpuContext,
    values: &[f64],
    params: &GridParams,
    isovalue: f64,
) -> Result<McOutput, String>

GPU dispatch for marching cubes isosurface extraction.

Each workgroup processes one voxel. The shader classifies corners, looks up the edge/triangle tables, interpolates edge vertices, and writes triangle data into an append-style output buffer.