a* pathfinding

I've tried to use the a* (a-star) algorithm before, only for it to become a terrible performance bottleneck.

Godot4's implementation works better out of the box than mine would work with years of tuning.

We're talking real proper map navigation, tied to a state machine.  hopefully the zombies become a bit more entertaining.

I can't promise a major AI overhaul in next weeks update, but I can promise an update.  the AI fork may take a couple of weeks to be ready for widespread use.

I also have some life commitments that may slow the release of some features.  Do not despair, weekly releases will continue... but some may be smaller than others, since I'm just one guy with a family and a career outside of game dev.