Function fors_sign 

pub fn fors_sign<P: Params>(
    md: &[u8],
    sk_seed: &[u8],
    pk_seed: &[u8],
    adrs_template: &Adrs,
) -> Result<Vec<u8>, SlhDsaError>

Sign a message digest using FORS.

Implements Algorithm 16 of FIPS 205. The message digest md contains k * a bits, which are split into k indices of a bits each. For each of the k FORS trees, the signature includes:

• The secret leaf value at the selected index (n bytes)
• An authentication path of a sibling nodes (a * n bytes)

The total FORS signature is k * (1 + a) * n bytes.

adrs_template is read-only — a local clone is taken internally for the scratch state mutated during signing. Returns Err(SlhDsaError::FaultDetected) only when sca-fors-indices-check (T1-E) is enabled and the integrity check on the FORS index vector fails; otherwise always Ok.