Add a temporary in-cell holding fallback for the single placed proxy actor when no valid same-cell remote player is available. Introduces kProxyHiddenHoldingPosition, ProxyLifecycleState, RemotePlayerSelection, MoveProxyToHoldingPosition and RestoreProxyForRemotePlayer, plus selection/state-tracking and throttled logs. The controller now moves the proxy to the hidden position on disconnect, disappearance, or cell-mismatch and snaps it back when a valid same-cell remote appears. Documentation and dev log updated to describe the lifecycle and rationale (docs/architecture.md, docs/dev-log.md, protocol/player-sync.md).
andrew
a0563a6849