session-foundation/session-router — reverse-engineered prompt

Build me this Session Router project from source and get it into a state where I can actually run it locally for development and basic testing. I want the core app working as an onion routed IP network component for private, low latency traffic, basically the networking layer used by Session.

Please set up whatever is needed so it compiles cleanly, starts without a lot of manual guesswork, and has sensible defaults or a simple development config. I would also like an easy way to confirm it is running correctly and routing traffic, plus a small set of clear notes or helper scripts for build, start, stop, logs, and common fixes if something goes wrong.

If there is a usable GUI in the repo, make that work too, but the main goal is a reliable working build and a simple way to use it. Use the project docs as the source of truth, and look up current docs online if you need to.