Is washing eggs before use a Sunnah definitively established from the Prophet, may God’s prayers and peace be upon him?

One must differentiate between innovation (bid‘ah) in religion and worldly matters. The religiously forbidden innovation is that which is introduced into acts of worship. As for washing an egg before use, there is no specific command or sunnah from the Prophet, peace and blessings be upon him, regarding it. It falls under the general evidence that encourages cleanliness and is considered a custom, not an act of worship.