Add comprehensive godoc documentation to handler.go

Expand documentation comments for SimpleHandler type and its methods
to better explain their purpose, parameters, and behavior.

internal/routewatch/peerhandler.go

@@ -47,7 +47,10 @@ type peerUpdate struct {
 	timestamp   time.Time
 }
 
-// NewPeerHandler creates a new batched peer tracking handler
+// NewPeerHandler creates a new PeerHandler with the given database store and logger.
+// It initializes the peer batch buffer and starts a background goroutine that
+// periodically flushes accumulated peer updates to the database. The handler
+// should be stopped by calling Stop when it is no longer needed.
 func NewPeerHandler(db database.Store, logger *logger.Logger) *PeerHandler {
 	h := &PeerHandler{
 		db:        db,
@@ -64,7 +67,9 @@ func NewPeerHandler(db database.Store, logger *logger.Logger) *PeerHandler {
 	return h
 }
 
-// WantsMessage returns true for all message types since we track peers from all messages
+// WantsMessage returns true for all message types since peer information
+// is extracted from every RIS message regardless of type. This satisfies
+// the MessageHandler interface.
 func (h *PeerHandler) WantsMessage(_ string) bool {
 	return true
 }