Saddle me Naturalist

Added: Saddle + ride deer (sneak up to saddle, empty hand to ride, WASD steering, charged leap on jump key, 1-block step-up, saddle drops on death, shears unsaddle, no despawning). Zebras tame + saddle in one saddle click; sneaking players don't spook them. Known issues (fixed later): saddles invisible, wild deer stopped fleeing players.