What always came to mind for me is an “engine wiring harness”. It’s responsible for getting power and data to all the right places without having to manually route cables around the engine / car.
If you google an image of it, maybe it’ll make sense
As already mentioned, this is the noun use but also different connotations.
To my thinking, to orchestrate or steer suggests a conductor or driver, an outside entity providing direction. A master agent creating and directing subagents could reasonably be called an orchestrator.
A harness is what the horse wears to pull a cart, or what connects a pilot to a parachute and provides the controls to tug on and steer. It might provide guidance or capability, but not active direction. It's also a fairly common use in hardware ( a wire harness) and software (a testing harness) already.
Well, "Orchestrate" and "Steer" are verbs, while "Harness" is a noun. You need a noun here, not a verb, because the harness is not actively doing anything, it's just a set of constraints and a toolset.
It took me some time to realise what people mean by it, originally confusing it with harvest.