refactor(evidence): unify formulas with typed evidence

harness/tests/test_evidence_formula_migration.py

@@ -0,0 +1,26 @@
+"""Migration boundary: legacy formulas become curated evidence or session proposals."""
+
+from tht.evidence import formula_store
+from tht.evidence.formula_store import ConceptFormula
+
+
+def test_reviewed_formula_migration_has_deterministic_provenance_hash():
+    formula = ConceptFormula(
+        concept="fascia pediatrica",
+        columns=["clinical.patient.birth_date"],
+        sql="CASE WHEN age < 18 THEN 'pediatrica' ELSE 'adulta' END",
+        status="reviewed",
+        sources=["Regola clinica approvata dal gruppo pediatrico."],
+    )
+
+    first = formula_store.legacy_formula_to_curated(
+        formula, legacy_path="formulas/fascia-pediatrica-1.sql.md",
+    )
+    second = formula_store.legacy_formula_to_curated(
+        formula, legacy_path="formulas/fascia-pediatrica-1.sql.md",
+    )
+
+    assert first is not None
+    assert second is not None
+    assert first.provenance.source_sha256 == second.provenance.source_sha256
+    assert first.provenance.source_sha256.startswith("sha256:")