The header wraps under 860px, so a menu-wrap can land at the start of a row.
`.popover` is right-anchored to its button, so the theme/language/account menu
rendered at x=-280 of a 390px screen — half of it off the left edge and its
buttons unclickable. Anchor the popover to the full-width header on narrow
screens instead.
Measured at 390x844 before/after: popover x=-280 → x=56, w=326, fully inside.
3dtours
c00c605dd7