Adding jQuery Tabs via template.php
hook_theme() is a hook that must returns the list of theme functions implemented by a module, or a theme.

Calling drupal_add_library() or drupal_add_js() inside hook_theme() is not the way to add a JavaScript file to a page.

As reported in Structure of the .info file, a theme can use the scripts directive to declare the JavaScript files that it uses. 

scripts[] = js/custom.js


Alternatively, a theme can use drupal_add_js() inside a theme function, or use the following snipped inside page.tpl.php, or any alternative page template Drupal would use.



drupal_add_js($path_to_script);
$scripts = drupal_get_js();