Ruby 4.0.0 Released

Ruby 4.0.0 has been released with two major experimental features: Ruby Box for isolating definitions (useful for monkey patches and parallel deployments) and ZJIT, a new JIT compiler that's faster than the interpreter but not yet production-ready. The release includes significant Ractor improvements for better parallelism, promotes Set and Pathname to core classes, adds new methods like Array#rfind and Math.log1p, and introduces Ractor::Port for inter-Ractor communication. Performance enhancements include faster Class#new, improved GC, and reduced lock contention. Breaking changes include removal of several deprecated Ractor methods and process creation via pipe syntax.