Transmission #051: Fix inventory tab row horizontal placement

Tab buttons were positioned with anchoredPosition.x = -tabRowW/2 + … while each tab already uses anchors on the tab row’s top-left; the row’s left edge is already at -tabRowW/2 in local space, so the extra -tabRowW/2 shoved the whole strip off the left. First-tab x now starts at panelMarginLeft inset from that edge only.