I'm trying to create a planetary system around a red dwarf star (M-class). The problem is that I'm not sure of a good size for the star to keep the star's habitable zone far enough away to prevent stellar weather from interfering with the planet, while still having an M-class star (e.g. Youtuber Artifexian suggests 0.6 M☉ as a lower bound, but this is still a K star). This would be less of an issue if a space-faring civilization were to simply establish colonies here, but my intent is to create a planet where intelligent life can evolve naturally.
TL;DR: What is the smallest possible size for an M class star capable of harboring a life-sustaining terrestrial planet?
Thanks in advance!