Stub l0 module in test so patch works without l0-python installed

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

Author: baogorek

tests/unit/calibration/test_unified_calibration.py

@@ -5,12 +5,24 @@
 block-level takeup seeding, county precomputation, and CLI flags.
 """
 
+import sys
+import types
+
 import numpy as np
 import pytest
 import scipy.sparse as sp
 from types import SimpleNamespace
 from unittest.mock import patch
 
+# Ensure `l0.calibration` is importable so patch() can traverse the path
+# even when the real l0-python package is not installed (e.g. CI).
+if "l0" not in sys.modules:
+    _l0 = types.ModuleType("l0")
+    _l0.calibration = types.ModuleType("l0.calibration")
+    _l0.calibration.SparseCalibrationWeights = None
+    sys.modules["l0"] = _l0
+    sys.modules["l0.calibration"] = _l0.calibration
+
 from policyengine_us_data.utils.randomness import seeded_rng
 from policyengine_us_data.utils.takeup import (
     SIMPLE_TAKEUP_VARS,