Production WS path now constructs RealParticipant + ScriptedBotParticipant
and hands them to BattleSessionV2 instead of the old single-WS
BattleSession. Wire behaviour preserved end-to-end (BattleNodeFlowTests
still pass).
Also fixes a RunAsync bug uncovered by the cutover: WhenAny would
terminate the session as soon as the scripted bot's no-op RunAsync
resolved, killing the live WS read loop before any traffic arrived.
Phase 1 semantics are simpler — wait for ALL participants. Phase 2's
Pvp disconnect propagation will revisit this.
91472df6fc