chore(set_theory/surreal/basic): Allow dot notation on `pgame.numeric` (#13768)
chore(set_theory/surreal/basic): Allow dot notation on `pgame.numeric` (#13768)

Rename `numeric_neg`/`numeric_add` to `numeric.add`/`numeric.neg`. Prove `numeric.sub` in passing.





leanprover-community/mathlib,leanprover-community/mathlib