Prevent TurnDirectory.StartFirstRound from firing multiple times

There appears to be a bug with the MissionControl (maybe?) implementation of additional lances. When the dropship lands, it looks like it invokes TurnDirector.OnDropshipAnimationComplete which ultimately ends up calling TurnDirector.StartFirstRound. This can lead to the round 'starting' multiple times.

We need to put a gate in on TurnDirector.StartFirstRound() to do nothing is GameHasBegun = true. Fix should be named something like 'PreventMultipleFirstRoundStarts'?

Start by tracing TurnDirector.OnDropshipAnimationComplete into TurnDirector.StartFirstRound and inspect how MissionControl handles additional lances. Verify the existing GameHasBegun state and ensure repeated first-round triggers are ignored; done means the first round starts only once.

Written by the indexing model from the issue text.