Function encode_ht_code_block_scalar 

pub fn encode_ht_code_block_scalar(
    coefficients: &[i32],
    width: u32,
    height: u32,
    total_bitplanes: u8,
) -> Result<EncodedHtJ2kCodeBlock, &'static str>

Adapter scalar HTJ2K cleanup-only encoder helper for backend experimentation.