Lean migration: typeclass-based parameter passing, as in the Agda original

The port had flattened Agda's instance arguments ({{flA}}, {{evaluator}},
{{latticeInterpretation}}, {{validEvaluator}}) into explicitly threaded
values (fhL, E, I, hE). Restore them as typeclasses:

- Spa.FiniteHeightLattice: now actually used — Fixedpoint takes the
  instance instead of a FixedHeight value; FiniteMap gets the missing
  instance (height = ks.length * height B), so varsFixedHeight /
  statesFixedHeight / signFixedHeight / constFixedHeight plumbing
  disappears (instance bottoms are defeq to the old ones)
- Spa.Analysis.Forward.Evaluation: StmtEvaluator/ExprEvaluator become
  classes; the Valid* Props become Prop-classes, as in Agda
- Spa.Analysis.Forward.Adapters: the expr→stmt adapter and its validity
  are instances (Agda: the ExprToStmtAdapter instances)
- LatticeInterpretation is a class; sign/const interpretations,
  evaluators and validity proofs are instances; use sites read like the
  Agda module applications: result SignLattice prog

Proof simplifications (same theorems, proofs factored):

- Spa.Lattice.AboveBelow.monotone₂_of_strict: any ⊥-strict/⊤-dominated
  operation on a flat lattice is monotone — replaces the four near-
  identical case bashes per analysis (postulates in Agda)
- Spa.Lattice.AboveBelow.interp_sup_of/interp_inf_of: the shared flat-
  lattice interpretation case analysis, making interpSign_sup/inf and
  interpConst_sup/inf one-liners

lake build green with zero warnings; lake exe spa output verified
byte-identical (diff) to the previous, Agda-verified output.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

lean/Spa/Lattice/FiniteMap.lean

@@ -639,6 +639,12 @@ def fixedHeight {hB : ℕ} (fhB : FixedHeight B hB) (ks : List A) :
       (ofIter ks) toIter (ofIter_monotone ks) toIter_monotone
       (toIter_ofIter ks) (fun fm => ofIter_toIter fm)).cast (by ring)
 
+/-- Agda: `isFiniteHeightLattice`/`finiteHeightLattice` of `Lattice/FiniteMap.agda`
+(there instance arguments; here an instance). -/
+instance [IB : FiniteHeightLattice B] : FiniteHeightLattice (FiniteMap A B ks) where
+  height := ks.length * IB.height
+  fixedHeight := fixedHeight IB.fixedHeight ks
+
 omit [Lattice B] in
 /-- Agda: `to-build`. -/
 theorem mem_ofIter_build {b : B} : ∀ {ks : List A} {k : A} {v : B},