ax(node): replace AddPeer prose comment with usage example

AX Principle 2: comments restate the signature — replace with a concrete
call showing realistic values and the debounce behaviour as a note.

Co-Authored-By: Charon <charon@lethean.io>

pkg/node/peer.go

@@ -232,9 +232,8 @@ func (r *PeerRegistry) ListAllowedPublicKeys() []string {
 	return keys
 }
 
-// AddPeer adds a new peer to the registry.
-// Note: Persistence is debounced (writes batched every 5s). Call Close() to ensure
-// all changes are flushed to disk before shutdown.
+// registry.AddPeer(&Peer{ID: "abc123", Name: "worker-1", Address: "10.0.0.2:9090", Role: RoleWorker})
+// Persistence is debounced — call Close() before shutdown to flush all pending writes.
 func (r *PeerRegistry) AddPeer(peer *Peer) error {
 	r.mu.Lock()