Function wots_sign_into 

pub fn wots_sign_into<P: Params>(
    m: &[u8],
    sk_seed: &[u8],
    pk_seed: &[u8],
    adrs: &mut Adrs,
    out: &mut [u8],
)

Streaming variant of wots_sign — writes the LEN * N-byte signature into the start of out (which must be at least that size) instead of returning a freshly-allocated Vec<u8>.

Used by the streaming sign path (xmss_sign_into → ht_sign_into → slh_sign_into) to avoid the transient per-layer heap buffers.