I can't speak for every therapist, but the ones I've had are pretty chill when it comes to SH. With my new t I said something along the lines of "I have urges to SH but I very rarely act on them" and then she asked about coping skills and suggested a few things. Every now and again she asks about it, especially if my mood is unstable, but she trusts me if I say I don't need to go to the hospital, and I trust her when she says I do, but this is when I have all sorts of symptoms going on in addition to SH.

As for bringin it up, you could be hypothetical like already mentioned, or you could just be straight forward and say something like "I have (occasional/frequent/constant/whatever) urges to self harm"