Tool contract 3.17.0

One grammar, one vocabulary (docs/reviews/2026-09-19-INTERFACE-REVIEW.md Part 2, Phase 4).

• Every windowed tool's applied.window says its season: season (the season the window starts in; null on an unbounded window), crosses (every season roll inside it, empty when clean) and season_age_days, on battles_query, battles_performance, battles_decks, battles_cards, battles_opponents, battles_compare, clans_standings, battles_levels, clans_pilot_scores, clans_participation, rankings_timeline, game_events and elixir_timeline, as the meta and series tools already carried them. The crossing note fires only when crosses is non-empty.
• The player battle tools and clans_standings take season ('current', 'previous', 2026-08 or 135), so "this season" is one argument on every tool that has a window; their default is unchanged.
• The series tools (players_timeline, clans_timeline, clans_members_timeline) accept an instant for from/to and floor it to its game day (10:00Z grid), echoing the instant under applied.window.floored with a note, where they refused it; days: N is N game days, today included.
• The one point vocabulary: players_timeline points carry day beside date; rankings_timeline points carry day (the snapshot's game day); battles_levels.monthly_trend marks the window's clipped months with partial: true and covers {from, to}, the weekly shape; clans_participation echoes applied.window.source: 'default' when weeks was defaulted and its notes say war_points is the period points figure; game_events carries game_days_seen beside days_seen (the same sightings on the game day grid; days_seen retires at 4.0.0), its running_on_latest_day is a fact of the table rather than of the window, and a date-only to no longer reaches one day past itself; clans_roster.lifetime carries profile_observed_at beside as_of (as_of retires at 4.0.0).
• clans_pilot_scores and battles_levels.monthly_trend take mean_starting_trophies over ladder battles only (a Path of Legends figure is a league rating on another scale; null with none), and say so.
• players_summary.top_deck and best_deck carry mean_level_gap, so the comparability note names real gaps.
• Descriptions: players_timeline.metrics names its four groups and the default; battles_performance.group_by says mode is the named game mode, not the group; clans_members_timeline.limit says the order and how to choose; rankings_players says rating is the profile's pol_trophies, verified equal on the live API.

Additive; no migration.