fix base costs and import backstage in ctm notebook

studies/202512_GenesysCX/ctm-token-calculator/tests/test_appendix4.py

@@ -106,3 +106,10 @@ def test_case_flows_and_kpis():
     inc2 = {y: -1.0 for y in a4.YEARS}
     net2 = {y: benefits[y] + 1.0 for y in a4.YEARS}
     assert a4.case_kpis(inc2, net2)["roi"] is None
+
+
+def test_contracted_overlays_verbatim():
+    assert a4.tco("ccaas_annual") == 3_200_000            # signed contract
+    assert a4.TCO_VERBATIM["ccaas_annual"] == 4_300_000   # deck record intact
+    assert a4.tco("current_annual") == a4.TCO_VERBATIM["current_annual"]
+    assert a4.licence_costs_by_year(12, a4.tco("ccaas_annual"))[2027] == 3_200_000