Fix pre-existing test failures from main

- Remove test_reproducibility.py: imports modules that never existed
  (enhanced_cps.imputation, enhanced_cps.reweight, scripts). Broken
  since PR #117 (July 2025), never caught because old testpaths
  didn't include top-level tests/.
- Fix test_legacy_target_overview_without_reform_id: create builder
  before installing legacy view so __init__'s create_or_replace_views
  doesn't overwrite it. Clear column cache so builder re-detects
  missing reform_id. Mirrors fix from unmerged PR #665.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: anth-volk

policyengine_us_data/tests/unit/calibration/test_unified_matrix_builder.py

@@ -277,8 +277,8 @@ def test_inactive_targets_are_excluded(self):
     def test_legacy_target_overview_without_reform_id(self):
         b = self._make_builder()
         _create_legacy_target_overview(self.engine)
+        b._target_overview_columns = None
         try:
-            b._target_overview_columns = None
             df = b._query_targets({"domain_variables": ["aca_ptc"]})
             self.assertGreater(len(df), 0)
             self.assertIn("reform_id", df.columns)