Is there such a thing as crackedglassroofapobia?? Cause if so...I now have it.
It's a mystery what did it. The car wasn't beneath anything when it happened, and we were traveling at low speed. The damage looked like a sharp rock fell directly on the glass from above. It left a spider crack about 1 inch in diameter in the top layer of the laminated glass, and a pimple-sized white spot in the center where the glass powdered.
I took the car to Safelite and they fixed it in about 30 minutes for $99 by injecting resin and polishing it. The result looks pretty good and most people would never see it. It looks like a small water spot now.
TIP: If you need to get a repair like this, be sure to specify it's a laminated glass roof, not a "sunroof". They can't repair sunroof glass because it's not laminated, and so glass shop staff may tell you it's not repairable.
Tesla gave me an estimate on replacing the roof glass, in case the repair doesn't last: $1055 parts, labor and tax.