unit tests (& some fixes)

uhhhh started adding actual unit tests… i was kinda putting it off but i gotta have it…

set up GoogleTest + CTest and started covering some stuff

• ECS registry / generational IDs
• entity UUIDs
• entity serialization
• hierarchy / parenting
• collision events + movement blocking
• save games
• maps

bugs bugs bugs…

and unsurprisingly, writing tests immediately started exposing some smaller issues.

fixed stale entity handles being able to mess with components belonging to a recycled entity slot, and cleaned up some hierarchy transform / rotation handling that wasn’t preserving transforms correctly in certain parenting cases.

also tightened up a couple math helpers while testing them.

im still gonna write even more tests.. its very needed at this point and will prolly help me find some more bugs i missed before…