patch: fix compatibility issue on node 23+ (including LTS version node 24)

reference tensorflow/tfjs#8425

Author: beenotung

polyfill.ts

@@ -0,0 +1,16 @@
+// Polyfill the removed util.isNullOrUndefined (Node 23+ broke tfjs-node < ~4.23)
+let util = require('util')
+
+// Only patch if the function is missing
+if (typeof util.isNullOrUndefined !== 'function') {
+  util.isNullOrUndefined = (val: any) => val === null || val === undefined
+}
+
+// Optional: also patch isUndefined / isDefined if you see similar errors later
+if (typeof util.isUndefined !== 'function') {
+  util.isUndefined = (val: any) => val === undefined
+}
+
+if (typeof util.isDefined !== 'function') {
+  util.isDefined = (val: any) => val !== undefined
+}

server.ts

@@ -1,3 +1,4 @@
+import './polyfill'
 import express from 'express'
 import { print } from 'listening-on'
 import { main as train } from './train'