ax(node): replace prose comments with usage examples (AX Principle 2)

Comments on saveNow, save, load, Close, and DefaultResponseHandler
restated what the signature already said. Replace with concrete call
examples showing how each is actually invoked.

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

pkg/node/peer.go

@@ -624,7 +624,7 @@ func (r *PeerRegistry) scheduleSave() {
 	})
 }
 
-// saveNow persists peers to disk immediately.
+// r.mutex.RLock(); err := r.saveNow(); r.mutex.RUnlock()
 // Must be called with r.mutex held (at least RLock).
 func (r *PeerRegistry) saveNow() error {
 	// Ensure directory exists
@@ -658,7 +658,7 @@ func (r *PeerRegistry) saveNow() error {
 	return nil
 }
 
-// Close flushes any pending changes and releases resources.
+// defer registry.Close() // flush pending writes on shutdown
 func (r *PeerRegistry) Close() error {
 	r.saveStopOnce.Do(func() {
 		close(r.stopChan)
@@ -684,15 +684,14 @@ func (r *PeerRegistry) Close() error {
 	return nil
 }
 
-// save is a helper that schedules a debounced save.
-// Kept for backward compatibility but now debounces writes.
+// r.save() // schedules a debounced write; errors logged asynchronously
 // Must NOT be called with r.mutex held.
 func (r *PeerRegistry) save() error {
 	r.scheduleSave()
 	return nil // Errors will be logged asynchronously
 }
 
-// load reads peers from disk.
+// if err := r.load(); err != nil { /* no existing peers, that's ok */ }
 func (r *PeerRegistry) load() error {
 	data, err := os.ReadFile(r.path)
 	if err != nil {

pkg/node/protocol.go

@@ -57,7 +57,7 @@ func (h *ResponseHandler) ParseResponse(resp *Message, expectedType MessageType,
 	return nil
 }
 
-// DefaultResponseHandler is the default response handler instance.
+// if err := ValidateResponse(resp, MsgPong); err != nil { return 0, err } // delegates to DefaultResponseHandler
 var DefaultResponseHandler = &ResponseHandler{}
 
 // if err := ValidateResponse(resp, MsgPong); err != nil { return 0, err }