Explain how Keyword Arguments are implemented internals and their historical evolution up to Ruby 3.

Ruby 3 completely separated keyword arguments from standard positional hashes, making signatures explicit and removing subtle argument conversion bugs.

In Ruby 2.x, keyword arguments were internally implemented as a trailing options hash. This design led to complex edge cases when mixing positional arguments, optional hashes, and keyword arguments, often requiring developers to use double-splat (**) hacks to ensure predictable behavior. Ruby 3 resolved this by completely separating positional and keyword arguments. Passing a hash to a method expecting keyword arguments now raises an ArgumentError unless you explicitly convert it using the ** operator.