Added sixteen-seat building garrisons

I added sixteen infantry seats to the Core and Barracks. Units can shelter inside these buildings and leave individually or through the all-occupant command.

The garrison interface remains available alongside production. Boarding, occupancy and disembarkation use native unit state, with saved occupants retained across a resumed game.

“Infantry can board and leave Core and Barracks while production remains available.”

The clips initialize an occupied Barracks, inspect its native seat grid and use the real single-seat and all-seat exit controls. They are a controlled garrison demonstration, not a filmed production cycle or defended battle.