river-breakout-tabs-wide-action-spacing.md

@primer/react-brand	patch

Updates to the RiverBreakoutTabs component:

• Reduced the spacing above the tab list action on wide breakpoints from 16px to 12px
• Reduced the gridline outer padding from 64px to 60px at the widest breakpoint
• Added a 0.3s transition to the tab heading color
• Fixed a shadow-border issue on hovered tab indicators. It now fills the entire parent space using a negative offset.