Actors occupying a cell should have selection boxes no larger than that cell + health bar moved lower slightly

There are two issues really;

1. Selection boxes of larger units are larger than an in-game cell, and as such 'overlap' horizontally with similar units to either side
2. Health bars are outside of a units selection box and float into the selection boxes of other units vertically above

Larger units currently have larger selection boxes which clip over other unit selection boxes. This means that such units that are horizontally adjacent have their health bars overlapping. For particularly 'large' units like the mammoth, you can have a unit take ~20% damage, but look like its at full health because of this overlap. Same for pips and passenger capacity.

Secondly, because the health bars of units are outside of the units selection box, when two units are vertically adjacent the health bar of the lower vehicle sites inside the selection box of the above vehicle. From a UI perspective this is slightly misleading.

As you can see, the med tank and heavys selection boxes overlap, and as such, so do their health bars.

I propose two changes to solve this;

1. Any actor that occupies an entire cell should have a selection box the exact size of that cell
2. The health bar should be lowered slightly to sit within the selection box

like so; (ignore the poorly cropped med)

selected

unselected

As you can see, when selected unit selection boxes (and health bars) no longer overlap. When unselected, there is at least a pixel of horizontal 'padding' between health bars.

No files or tests are named. Use the screenshots and the two proposed behavior changes as acceptance criteria, then locate the actor selection-box and health-bar rendering entry points and reproduce the overlap with horizontally and vertically adjacent units. Done means cell-sized selection boxes for full-cell actors and health bars contained within their selection boxes without misleading overlap.