The three PvP BattleNodeFlowTests drove each client's handshake to Ready
independently; the new barrier withholds Ready until both sides swap, so the
single-client helper timed out. Split DriveHandshakeAsync into DriveThroughSwapAsync
(stops at SwapResponse) + DrivePvpHandshakeAsync (drives both, then drains the
barrier-released Ready for each). Scripted/Bot single-client paths are unaffected
(non-IHasHandshakePhase opponent releases Ready immediately).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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