jedi return [
(new Extend\Frontend('forum'))
->js(DIR.'/js/forum.js')
->css(DIR.'/resources/less/forum.less'),
(new Extend\Frontend('admin'))
->js(DIR.'/js/admin.js')
->css(DIR.'/resources/less/admin.less'),
new Extend\Locales(DIR . '/resources/locale')
];
This is odd, you are looking at the wrong file, the error mentions the right directory:
jedi C:\wamp64\www\bek\workbench\batman\js\dist\forum.js
Your extend misses dist, try this:
<?php
return [
(new Extend\Frontend('forum'))
->js(__DIR__.'/js/dist/forum.js')
->css(__DIR__.'/resources/less/forum.less'),
(new Extend\Frontend('admin'))
->js(__DIR__.'/js/dist/admin.js')
->css(__DIR__.'/resources/less/admin.less'),
new Extend\Locales(__DIR__ . '/resources/locale')
];