Function decode 

pub fn decode(
    input: &[u8],
    params: AecParams,
    output_samples: usize,
) -> Result<Vec<u8>, AecError>

Decode an AEC bitstream into packed sample bytes.

• input: CCSDS/AEC payload bitstream.
• params: bit width, block size, RSI, and flags.
• output_samples: number of samples expected in the output.

Returns a Vec<u8> of length output_samples * bytes_per_sample, where bytes_per_sample = ceil(bits_per_sample / 8).

Note: When AecFlags::MSB is set, samples are written big-endian (MSB-first) per sample; otherwise little-endian.