fix(docs): update phase1 plan attestation examples to pipe delimiters

Example code in the implementation plan still used colon delimiters.
Updated all attestation format strings and assertions to use pipes,
matching the actual implementation.

Author: TheCryptoDonkey

docs/plans/2026-03-31-heartwood-phase1.md

@@ -798,8 +798,8 @@ fn blind_proof_round_trip() {
     assert!(proof.purpose.is_none());
     assert!(proof.index.is_none());
 
-    // Attestation format: "nsec-tree:own:{master_hex}:{child_hex}"
-    assert!(proof.attestation.starts_with("nsec-tree:own:"));
+    // Attestation format: "nsec-tree:own|{master_hex}|{child_hex}"
+    assert!(proof.attestation.starts_with("nsec-tree:own|"));
     assert_eq!(proof.signature.len(), 128); // 64 bytes as hex
 
     // Verify
@@ -818,9 +818,9 @@ fn full_proof_round_trip() {
     assert_eq!(proof.purpose.as_deref(), Some("social"));
     assert_eq!(proof.index, Some(0));
 
-    // Attestation format: "nsec-tree:link:{master_hex}:{child_hex}:social:0"
-    assert!(proof.attestation.starts_with("nsec-tree:link:"));
-    assert!(proof.attestation.ends_with(":social:0"));
+    // Attestation format: "nsec-tree:link|{master_hex}|{child_hex}|social|0"
+    assert!(proof.attestation.starts_with("nsec-tree:link|"));
+    assert!(proof.attestation.ends_with("|social|0"));
 
     // Verify
     assert!(verify_proof(&proof).unwrap());
@@ -833,7 +833,7 @@ fn tampered_attestation_fails_verification() {
     let child = derive(&root, "social", Some(0)).unwrap();
 
     let mut proof = create_blind_proof(&root, &child).unwrap();
-    proof.attestation = "nsec-tree:own:0000:0000".to_string();
+    proof.attestation = "nsec-tree:own|0000|0000".to_string();
 
     assert!(!verify_proof(&proof).unwrap());
 }
@@ -860,7 +860,7 @@ pub fn create_blind_proof(
     let master_hex = master_hex_from_root(root)?;
     let child_hex = bytes_to_hex(&child.public_key);
 
-    let attestation = format!("nsec-tree:own:{}:{}", master_hex, child_hex);
+    let attestation = format!("nsec-tree:own|{}|{}", master_hex, child_hex);
     let signature = sign_attestation(root, &attestation)?;
 
     Ok(LinkageProof {
@@ -882,7 +882,7 @@ pub fn create_full_proof(
     let child_hex = bytes_to_hex(&child.public_key);
 
     let attestation = format!(
-        "nsec-tree:link:{}:{}:{}:{}",
+        "nsec-tree:link|{}|{}|{}|{}",
         master_hex, child_hex, child.purpose, child.index
     );
     let signature = sign_attestation(root, &attestation)?;