No, yeast is not necessary in the batter for gingerbread cookies. Traditional gingerbread cookies do not typically require yeast. The leavening agents used in gingerbread cookies are usually baking soda and/or baking powder, which help them rise slightly and create a softer texture.
Yeast is commonly used in bread recipes to create a significant rise and develop a light, airy texture. However, in the case of gingerbread cookies, they are typically meant to be denser and chewier, so yeast is not needed.
By following a recipe that includes the appropriate amount of baking soda and/or baking powder, you can achieve the desired texture for gingerbread cookies without the use of yeast.