refactor(werkbank): extract soft-PLC provisioning + ICS probe into werkbank-exec (WB-04a) (#208)

werkbank-exec/src/fingerprint.rs

@@ -0,0 +1,32 @@
+//! Finding fingerprint helper (a SHA-256 over the salient parts), shared by the
+//! probe modules for stable dedup keys. Mirrors the agent's `dedup` helper.
+
+use sha2::{Digest, Sha256};
+
+/// A stable fingerprint over the given parts (order-sensitive, separated so
+/// `["ab","c"]` and `["a","bc"]` differ).
+pub fn compute_fingerprint(parts: &[&str]) -> String {
+    let mut hasher = Sha256::new();
+    for part in parts {
+        hasher.update(part.as_bytes());
+        hasher.update(b"|");
+    }
+    hex::encode(hasher.finalize())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn deterministic_and_hex() {
+        let a = compute_fingerprint(&["repo", "rule", "1"]);
+        assert_eq!(a, compute_fingerprint(&["repo", "rule", "1"]));
+        assert_eq!(a.len(), 64);
+        assert!(a.chars().all(|c| c.is_ascii_hexdigit()));
+        assert_ne!(
+            compute_fingerprint(&["ab", "c"]),
+            compute_fingerprint(&["a", "bc"])
+        );
+    }
+}