Brief observations:

- When a unit is standing on an improvement you cannot access the button to build on that improvement without moving the unit off it first.  Unless that's intended behavior, the action to build the improvement should probably be added to the action list for the unit on the tile.

- The newly-added hero action button that accesses hero inventory (from the appearance, "camp" or the like) does not have a tooltip on mouseover explaining the button's purpose.