* feat(mobile): split controls into separate Agent and Model buttons - Add MobileAgentButton with tap-to-cycle and long-press-to-open behavior - Add MobileModelButton for direct model panel access - Remove agent selection from UnifiedControlsDrawer for cleaner mobile UX - Agent cycling accessible via Tab key shortcut * fix(mobile): optimize controls layout and touch handling --------- Co-authored-by: Jovines <jovines@qq.com>