Unexplained brake noises

My 03's brakes have recently developed a noise on the front passenger side that I've not been able to explain so far

When I'm driving normally, It makes a squeaking noise that happens once per wheel rotation. When I hit the brakes, there's a single loud squeaking noise when I hit the brakes hard enough to come to a full stop.

I know its brakes because the bearing is fine, no slop, consistent force needed to spin the wheel.

I'm planning to pull the brakes off when I replace the front shocks and springs to see if something is obviously wrong, but I know the pads have nearly 1cm of pad width, the rotors are smooth enough, though there's a couple fine grooves in the outer face. They don't appear to be warped either. I feel like I've lot a little brake force recently, but not much at all.

Is there something specific I should look for here? I've not really experienced a noise like this in other cars.

 

I’ve got no idea why the noise was happening now. I took them apart, cleaned everything, greased everything, and put them back together. It stopped after that. There’s no obvious wear from anything rubbing that shouldn’t.