Have LatticeInterpretation extend Interp

LatticeInterpretation now extends Interp L (Value → Prop), so each analysis
defines only its LatticeInterpretation instance and gets the ⟦⟧ notation for
free. Drops the standalone per-analysis Interp instances (signInterp and the
anonymous constInterp). The Interp class is kept for other uses.

The interp*_mk_disjoint bootstrap lemmas now state on the raw interp function
since they feed the instance and run before any Interp instance exists; the
trivial sup/inf wrappers are inlined into the instance.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

lean/Spa/Language/Semantics.lean

@@ -1,5 +1,6 @@
 import Spa.Language.Base
 import Spa.Lattice
+import Spa.Interp
 
 namespace Spa
 
@@ -56,8 +57,7 @@ inductive EvalStmt : Env → Stmt → Env → Prop
       EvalExpr ρ e (.int 0) →
       EvalStmt ρ (.whileLoop e s) ρ
 
-class LatticeInterpretation (L : Type*) [Lattice L] where
-  interp : L → Value → Prop
+class LatticeInterpretation (L : Type*) [Lattice L] extends Interp L (Value → Prop) where
   interp_sup : ∀ {l₁ l₂ : L} (v : Value),
     interp l₁ v ∨ interp l₂ v → interp (l₁ ⊔ l₂) v
   interp_inf : ∀ {l₁ l₂ : L} (v : Value),