d665f88067
Single RegisterBattle(p1, p2?, type) with contract validation throws on invalid combinations (Pvp requires both; Bot requires p2==null; Scripted accepts either). PendingBattle carries Type + P1 + nullable P2. Handler + controller adapt; v1.2 behaviour preserved because Scripted is the only type used today (Phase 2 adds Pvp, Phase 3 adds Bot).