Tool contract 6.31.0

The battle tools, after the Elixir Gym's second run on them (feedback #148-#151).

• battles_meta_decks and battles_meta_cards apply the meta population (no event content, only decks the player chose) on every window. Before, a custom window or a segment read raw had kept both, which disagreed with the season rollup. mode: "event" there answers empty with a note, not a silent zero (#148).
• mode is event-aware everywhere: battles_trends, cards_synergy, the card profile and battles_opponents filter event battles by their event tag, and battles_cards labels them event, not casual (#148).
• battles_query deck_stats counts the battles this call matches (its window, mode and filters), the same set as total_count. It had counted the deck's lifetime whatever the window said. It is now declared in the output schema (#149).
• A note says when rows carry no tower level (river race rows record no support cards), so their towers may have started unequal and vs.tower_hp is not a margin of victory (#150).
• A too-large refusal on a one-size tool no longer advises compact or quotes the verbosity, and an unknown-argument refusal lists verbosity among the known arguments (#151).

Corrected values: deck_stats, and the meta tools on raw windows now exclude what the season rollup excluded.