Could be from a neighborhood cat. Also, check along your commute and make sure you aren’t accidentally brushing past any low hanging vegetation. Looks like a pattern in a very similar location so you could be unknowingly getting some brush or a branch along a normal drive you take.

Looks like extra casting material. You can either sand that down with an orbital and 90 grit - or let your pads get rid of it the first time you step on the brakes.