Function dct8x8_blocks_to_dwt53_float_linear_with_scratch 

pub fn dct8x8_blocks_to_dwt53_float_linear_with_scratch(
    blocks: &[[[f64; 8]; 8]],
    block_cols: usize,
    block_rows: usize,
    width: usize,
    height: usize,
    scratch: &mut Dct53GridScratch,
) -> Result<Dwt53TwoDimensional<f64>, Dct53GridError>

Map an adjacent 8x8 DCT block grid directly into a linearized one-level 2D 5/3 result using caller-owned scratch for reusable weight rows.