package!: set new Node version minimum

breaking change

engine-requirements.js

@@ -0,0 +1,10 @@
+const major = parseInt(process.versions.node.split('.')[0], 10);
+
+if (major < 20) {
+  console.error(
+    `\n❌ This package requires Node.js 20+ to run reliably.\n` +
+    `   You are using Node.js ${process.versions.node}.\n` +
+    `   Please upgrade to Node.js 20+ to proceed.\n`
+  );
+  process.exit(1);
+}