Function execute_slice 

pub unsafe fn execute_slice(
    src: usize,
    dst: usize,
    in_dims: &[u32],
    axis: usize,
    start: usize,
    len: usize,
    step: i64,
    elem_bytes: usize,
    base: *mut u8,
)

Output-indexed strided slice over the shared arena (mirrors execute_reverse). out[..,j,..] = in[.., start + j*step, ..] along axis (step may be negative). Byte-generic.