Struct BackgroundMenu

internal/app/menu.go:155–162

--- background picker ------------------------------------------------- BackgroundMenu is the stateful background picker. nil on model = closed. Two independent axes: a cork on/off toggle (row 0) and the fill color (the BackgroundColors rows, then a custom-hex row). Row layout: 0

//	1 .. len(colors)      → color rows (color index = cursor-1)
//	len(colors)+1         → custom hex
type BackgroundMenu struct {
	Cursor int
	Saved  Background // background at open time; restored on esc

	Cork  bool   // working cork toggle
	Color string // working fill color (hex, or "" for transparent)
	Hex   string // custom-hex buffer, e.g. "#1c2233"
}

func NewBackgroundMenu(current Background) *BackgroundMenu {
	m := &BackgroundMenu{