Train unit queue uses first building's queue to determine "full"

It seems that train unit queues are not working as expected. If I have three barracks selected and repeatedly issue the "train marine" command it seems that the queues for each building will increment in a balanced manner until the queue of the first selected barracks is full. At this point the remaining barracks will not add more units to the queue, instead they must wait until the first barracks finishes training a marine.

No file, test, or entry point is named. Start by locating the protocol definitions for the train-unit command and queue-related data, then determine whether the behavior can be represented or tested in this repository; done means confirming the intended queue behavior and identifying a concrete protocol-level change or documenting that it belongs elsewhere.

Written by the indexing model from the issue text.