@vttforge/core / registerSystem
Function: registerSystem()
registerSystem(
config):SystemRegistration
Register a Foundry system with VTTForge. Idempotency: the same id calling twice throws VTTF-0001, almost always a hot-reload or duplicate import bug.
Returns the registration object so consumers can inspect what was applied (useful in tests). The actual CONFIG mutations are deferred until Foundry's init hook fires.