A soulknife's mind blade is "identical in all ways (except visually) to a short sword". A short sword is a manufactured weapon, so a mind blade therefore counts as one. Plus, you get iterative attacks with it, unlike with natural weapons.
It does also mention that they count as magic for purposes of overcoming DR. That may be enough to allow them to be enchanted through Kensai as if MW, but YMMV.