Excavators should also dig from adjacent tiles when target tile is empty mid-dig

I think this could be achieved by checking how much material is in the tile when an Excavator picks a target tile, if it's less than the Excavator's bucket capacity, then quietly check and queue up neighbouring tiles, add their material to the total until it is more than the bucket size or there's no more valid adjacent tiles. Then whilst the Excavator does the dig animation, material is removed in queue order so that, at minimum, the target tile becomes mined.

I think even a "bonus range" of 1 tile would be fine, maybe more, *especially* for the Mega Excavator. The size of their bucket would make it look like the Excavator dug from that tile anyway, whilst greatly reducing the number of non-full scoops. It may even be disabled for the Small Excavator if its physical bucket size is deemed too small (but it's basically a non-issue for it anyway).

Extra: The reverse could be used for smoother dumping, stopping Trucks and their truck beds from stuttering about when a dump tile gets filled temporarily but then opens up as material falls away, but it's much less of an issue/annoyance.