Function tac_bytes 

pub fn tac_bytes(
    data: &[u8],
    separator: u8,
    before: bool,
    out: &mut impl Write,
) -> Result<()>

Reverse records separated by a single byte. Uses forward SIMD scan (memchr_iter) to collect all separator positions, then fills output buffer in reverse order with parallel copy for large data. Single write_all at the end for minimum syscall overhead.