A milestone email opens the battle that did it

When a milestone email names the battle that took you to a new arena or league, See the battle now opens that battle's own page, the same link an agent gets from battles_query. Its button, and the button on Your week in the Arena, now open your season on Ladder, and the Arena week's deck links every deck of the season on Ladder's Decks. The footers of the Top 100 and Card of the Week name the switch they turn off. Who gets each email and when is unchanged. No change to the tools.