The chance that any significant damage happened -- anything you'd ever notice -- is vanishingly slim. The fact that you stayed at an idle and it was less than minute . . . I've seen motors subjected to a lot worse than that and they survived just fine.Pulled the stupidest stunt I've ever done in my life after 51 years of wrenching on bikes. Details not important, but started my bike without any oil in it and ran it for about 30-45 seconds. During this time I put it into and out of 1st gear a couple times, and ran it mostly at idle before I realized my error and quickly shut it off.
I filled it with oil after this, ran it for five minutes. Dumped the new oil and refilled again. I checked my magnetic drain plug and it showed no metal particles. The bike seems to sound fine while running with no evident problems.
What are the chances I've done some long term damage to the motor?
Ride it, don't worry about it.