Function compute_sha256 

pub fn compute_sha256(canonical: &str) -> Sha256

Computes SHA-256 hash from a canonical string.

Returns the hash in format: sha256:<64 lowercase hex chars>.

Example

use northroot_proof_engine::hash::compute_sha256;

let canonical = r#"{"key":"value"}"#;
let hash = compute_sha256(canonical);
assert!(hash.starts_with("sha256:"));
assert_eq!(hash.len(), 71); // "sha256:" (7) + 64 hex = 71