akka/akka-core ? reverse-engineered prompt

Build me a simple end to end demo in this repo that shows what Akka is for, something like a small resilient service that can handle lots of messages, keep running if one part fails, and scale out across multiple nodes.

I’d like it to use the actor based style Akka is known for, and if it makes sense, show basic clustering and a streaming example too. Keep the example realistic and easy to follow, maybe a tiny order processing or chat style service with a few components talking to each other. Add a clear way to run it locally, a couple of tests that prove it works, and short notes in the README on how to start it.

Please make the code clean and idiomatic, and look up current docs online if you need to.