the client sends EndClientTurnMessage during the battle too, but its
tick and checksum belong to the battle, not to the home. we kept
comparing them against the home checksum and answered with
OutOfSyncMessage, which is the "Client and server are out of sync!"
dialog on tick 60.
HomeMode carries the stopped flag now and returns an empty turn result
while it is set, and sector_state_for raises it, so both the mission and
the matchmaking entry points are covered.
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