Drop the '/menu' functionality in favor of making that the 'restaurant_item' post type archive.  URL structure is now:
/menu
/menu/items/slug
/menu/tags/slug
Use the 'restaurant_item' post type 'archive_title' label.
Clean up conditionals and drop stuff we don't need.
Drop the default-filters.php file and move remaining filter to core.php.
Remove commented out code from post-types.php.
Revamp and clean up the admin.
Comments.  Comments.  Comments.  You know, so folks can understand the code better.
Rename admin.php to class-restaurant-admin.php.
Addition of a settings page.  Plus, a lot of admin screens wrangling.  This is starting to look like an actual restaurant plugin now.
Add missing inline comments.
Update admin bar label just so there's no confusion about what "menu item" means.
readme.md updates to reflect the code.