reactivecocoa/reactiveswift ? reverse-engineered prompt

Build me a Swift library for working with streams of values over time, like a cleaner way to handle callbacks, notifications, delegate style events, futures, and observable state.

I want the core pieces to feel easy to use and compose, with solid operators for transforming, combining, and filtering values. It should work on Apple platforms and Linux, be usable through Swift Package Manager, and also have support for Xcode, CocoaPods, and Carthage.

Please include good tests, clear docs, and a small playground or examples that show how to use the main ideas in real app situations. If you need to check current Swift or platform docs while building, go ahead and look them up online.