Contract 7.2.7

The new-user journey before beta (feedback #348, #349).

• battles_meta_decks rows with 2-5 players carry top_player_battles, the busiest player's battles, and a note names each row one player carries (80% or more of its battles). min_players: 2 let a 57-0 run read as "3 players, 57-2", the answer a "what deck should I play" read would lead with (#348).
• battles_meta_cards without fit_for no longer points at a decks[] it does not have.

Additive.