fix: redact PGP RSA binary lengths in snapshot for cross-platform compat

RSA PGP key binary lengths may differ between Windows and Linux due to
platform-specific PGP key serialization. Redact these values to prevent
cross-platform snapshot failures during mutation testing.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: EffortlessSteven

crates/uselesskey-pgp/tests/snapshots/snapshots_pgp__pgp_rsa_2048_shape.snap

@@ -9,5 +9,5 @@ user_id: snapshot-rsa2048 <snapshot-rsa2048@uselesskey.test>
 fingerprint_len: 40
 private_armored_starts_with: "-----BEGIN PGP PRIVATE KEY BLOCK-----"
 public_armored_starts_with: "-----BEGIN PGP PUBLIC KEY BLOCK-----"
-private_binary_len: 1303
-public_binary_len: 652
+private_binary_len: "[RSA_PRIV_LEN]"
+public_binary_len: "[RSA_PUB_LEN]"

crates/uselesskey-pgp/tests/snapshots_pgp.rs

@@ -60,7 +60,10 @@ fn snapshot_pgp_rsa_2048_shape() {
         public_binary_len: kp.public_key_binary().len(),
     };
 
-    insta::assert_yaml_snapshot!("pgp_rsa_2048_shape", result);
+    insta::assert_yaml_snapshot!("pgp_rsa_2048_shape", result, {
+        ".private_binary_len" => "[RSA_PRIV_LEN]",
+        ".public_binary_len" => "[RSA_PUB_LEN]",
+    });
 }
 
 #[test]