use node: prefix for requires

mostly because code is being autogenerated by all the AI stuff using
this prefix. it's also used in the stack trace.

src/hat.js

@@ -2,7 +2,7 @@
 
 exports = module.exports = hat;
 
-const crypto = require('crypto');
+const crypto = require('node:crypto');
 
 function hat(bits) {
     return crypto.randomBytes(bits / 8).toString('hex');