Prove the fundamental theorem

theories/soundness.v

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+Require Import Autosubst2.fintype Autosubst2.syntax.
+Require Import fp_red logrel typing.
+From Hammer Require Import Tactics.
+
+Theorem fundamental_theorem :
+  (forall n (Γ : fin n -> PTm n), ⊢ Γ -> ⊨ Γ) /\
+  (forall n Γ (a A : PTm n), Γ ⊢ a ∈ A -> Γ ⊨ a ∈ A)  /\
+  (forall n Γ (a b A : PTm n), Γ ⊢ a ≡ b ∈ A -> Γ ⊨ a ≡ b ∈ A).
+  apply wt_mutual; eauto with sem;[idtac].
+  hauto l:on use:SE_Pair.
+Qed.