RealParticipant gains _sessionFinished TCS + MarkSessionFinished /
AwaitSessionFinishedAsync. PvP first-arriver's handler awaits the
signal instead of calling self.RunAsync (which the session does
internally on the same instance — double-call would race the WS read).
BattleSession.RunAsync branches on Type: Pvp uses WhenAny + synthesize
BattleFinish(Win) to survivor + WhenAll(drain); Scripted/Bot keep
Phase 1's WhenAll-everything semantics. Disconnect cascade now drives
end-of-battle when a WS drops without a graceful Retire.
Internal setter; defaults to AwaitingInitNetwork. PvP needs A and B to
progress through the handshake states independently, which the
session-level BattleSession.Phase can't model. Session migration to read
realFrom.Phase is the next task.
Old single-WS BattleSession + its dispatch/pump/ClipAckArg tests are
obsolete after the Task 9 handler cutover. ClipAckArg overflow + boundary
coverage moved into RealParticipantTests. BattleSessionV2 renamed back
to BattleSession; the V2 suffix was a placeholder during the parallel
-build refactor.
Lifts the WS read loop, SIO encode/decode, per-WS OutboundSequencer +
InboundTracker, and SIO ack out of BattleSession into a participant.
PushAsync(noStock=false) assigns playSeq via the sequencer; noStock=true
bypasses it. FrameEmitted fires on each deduplicated inbound envelope.
The existing BattleSession keeps its own copy of the WS code for now;
Task 9 cuts the handler over to use BattleSessionV2 + RealParticipant
and Task 10 deletes the old BattleSession + duplicate code.