op-node: Improve CLI usage and inline err check

op-node/flags/flags.go

@@ -63,7 +63,7 @@ var (
 	}
 	RPCAdminPersistence = &cli.StringFlag{
 		Name:    "rpc.admin-state",
-		Usage:   "File path used to persist state changes made via the admin API so they persist across restarts",
+		Usage:   "File path used to persist state changes made via the admin API so they persist across restarts. Disabled if not set.",
 		EnvVars: prefixEnvVars("RPC_ADMIN_STATE"),
 	}
 	L1TrustRPC = &cli.BoolFlag{

op-node/node/config_persistence.go

@@ -71,8 +71,7 @@ func (p *ActiveConfigPersistence) persist(sequencerStarted bool) error {
 		return fmt.Errorf("open file (%v) for writing: %w", tmpFile, err)
 	}
 	defer file.Close() // Ensure file is closed even if write or sync fails
-	_, err = file.Write(data)
-	if err != nil {
+	if _, err = file.Write(data); err != nil {
 		return fmt.Errorf("write new config to temp file (%v): %w", tmpFile, err)
 	}
 	if err := file.Sync(); err != nil {