Add fail-closed source class and SAM fallback filters

backend/tests/test_sam_roof_label_refinement.py

@@ -31,3 +31,9 @@ def test_plausible_refinement_is_fail_closed() -> None:
 def test_yolo_round_trip_shape() -> None:
     line = MODULE.yolo_line((10.0, 20.0, 30.0, 40.0), 100, 100)
     assert line == "0 0.20000000 0.30000000 0.20000000 0.20000000"
+
+
+def test_cli_exposes_explicit_fallback_policy() -> None:
+    source = SCRIPT.read_text(encoding="utf-8")
+    assert 'choices=("retain", "drop")' in source
+    assert '"dropped_fallback_label_count"' in source