Function decode_block_range 

pub fn decode_block_range(
    data: &[u8],
    start_block: usize,
    end_block: usize,
) -> Result<Vec<i64>, CodecError>

Decode a range of blocks [start_block..end_block) from encoded data.

More efficient than calling decode_single_block repeatedly — scans headers once to find start_block, then decodes contiguously.