Tool contract 11.15.0

A sitting on the timeline names each trophy mode's own net, so a Path of Legends or seasonal Trophy Road sitting no longer reads as flat beside battles_performance (feedback #381, #382).

• elixir_timeline: battle_session (schema 3) and session_standout (schema 4) gain facts.trophy_net_by_mode, each mode group's net for the groups whose battles reported a trophy_change (ladder, ranked, event). trophy_net and trophy_net_peak stay Trophy Road's alone, and the trophy rungs still read them; battles_performance's net_trophies over the same window is the sum of trophy_net_by_mode.

Additive. JSON API unchanged.