v1.4.1 - subtotal on mobile; correct false root-cause comment

Subtotal now renders at all widths. Removes the 768px hide rule and the comment justifying it, which asserted a cart/hamburger crowding conflict that was never observed and never real. The hamburger was missing because header_mobile_items held the invalid element key mobile-toggle instead of popup-toggle; Kadence silently skips unrecognised keys.