One of my biggest questions about the forged about is what kind of CI (and somewhat CD) do they offer?

What can I expect as a developer using Tangled to build (and deploy) my app? What is the native platform? What are typical other CI systems that have been adapted to work on Tangled (Dagger, Drone, whatnot, especially if there are repos to demonstrate the adaption)? What can I expect as enterprise or lone developer using Tangled or self-hosting or federation?

The system is called Spindle, but what about it? What does it take inspiration from, what are things like it that would help us spool up on this?

Tangled has its own CI named Spindle. However it is not limited to that as there is for example https://tangled.org/mitchellh.com/tack which allows connecting different CIs to Tangled.