When I play strategy games against the computer I am always amazed that no one does a simple for loop through the enemy units to see if they're literally just outside my city, base, planet, whatever ready to attack.

That's what we humans tend to do.  The most lethal strategy in these kinds of games is usually to line up our units, ready to attack and then WHAM, knock down the AI in a couple of lethal turns.

In GalCiv, there is also the influence attack -- building influence base after influence base and gobble up the galaxy.

In GalCiv I, the AI did monitor this stuff and would come up with some funny responses like "Just so you know, we know what you're doing.."  In the original OS/2 version, the AI would surround your ships with stealth ships (the OS/2 verison had cloaked ships but they weren't very fun which is why they're not in now) then it would determine when it had enough and then preemptively attack you.

I don't know if I'll have enough time to put in cool stuff like having AI ships surround your ships.  That's the goal.  But the AI does get a pretty good picture of what the human player is up to (at higher difficulty levels) and start to put together a response to it even if it's not apparent.