Stop "jumpy" windows (and show number of trucks assigned)

CoI windows often change height when some things happen, like if I assign more trucks to a Tree Harvester or Mind Control Tower. This causes the "add more" button to move up, so that it's no longer under my mouse cursor, meaning I have to move my mouse cursor to keep adding more trucks.
That behaviour is objectively bad UI design. User interfaces should *never* behave like this!
Another thing is that I don't like having to count my trucks to know how many I've assigned. Like if I've assigned 30 or 40, I have to count the number of lines of trucks and then to mental arithmetic. The game ought to show me a numerical value, in addition to the visual representation of the number of trucks.

See issue #612 that I opened on Github.