Foundation for the aego engine.
core/ errs, log, handle arena, mathx, clock, stats
platform SDL3 backend plus a headless one, input state, events
gpu device abstraction with gl33 and null backends
vfs scheme-based virtual filesystem with overlay mounts
engine builder, module registry, phase-ordered system loop, jobs
demos basic, resize, input, headless; sandbox driver
OpenGL bindings are generated into gpu/gl33/gl by tools/gen-gl.sh,
so the module has no external dependencies.