Reset sim thermocouple (or cool naturally) when in idle with simulation mode

[solnus]

When running with sim mode, the temp reaches the target and never resets, disallowing running another simulated schedule without restarting the service. I would propose one of two approaches - either just reset to environment temp after reaching idle, or continue "natural" cooling rate even in idle (with speedup factor accounted for).

[jbruce12000]

super low priority. work-around is to re-start the process. most folks will simulate to decide whether to use the software or not - assess features, and then move on to the work of implementing the hardware.

PR welcome. this should be just a few line change I'd expect.

[solnus]

Agree low priority, just want to track it. I may get to it eventually but not currently familiar enough with the code base to find the right place to do it.