Keep account controls and battle decks within small screens

On the smallest phones, the top bar keeps its logo, full product label and account control within the screen. Long account names wrap in the menu. On narrow phones, battle decks stack while keeping their two rows of four cards, and player names have room beside the you badge. Larger phones and desktop keep their paired decks. MCP 11.2.3 and JSON API 3.0.0 unchanged.