Does a resolver distinguish between negative and positive angles?
First, resolvers don't care about positive and negative. The two outputs are sine waves at the reference frequency (classically 400 Hz), amplitude modulated with the sine and cosine of the shaft angle.

Standard resolver-to-digital decoder modules produce a binary word which varies from 0...0 to F...F over 360 degrees (or 2pi radians, take your pick). How you treat this number (0 to 2 pi, or -pi to pi) is entirely up to you.

Assuming a 0 to 2 pi representation, the second angle will not be interpreted as -pi/4, but rather as 1.75 pi. Of course, you are free to add whatever offsets you like.