migrate to "export default"

also, set no-use-before-define in linter

src/test/syslog-test.js

@@ -7,7 +7,7 @@ import net from 'node:net';
 import path from 'node:path';
 import paths from '../paths.js';
 import safe from 'safetydance';
-import * as syslogServer from '../../syslog.js';
+import syslogServer from '../../syslog.js';
 import timers from 'timers/promises';
 
 /* global describe:false */