Store SPM geographic adjustments instead of thresholds

[MaxGhenis]

Summary

• Stop materializing CPS/local spm_unit_spm_threshold values in us-data.
• Store spm_unit_geographic_adjustment inputs from CPS SPM_GEOADJ and assigned local/CD geography instead.
• Remove duplicated SPM threshold/reference-threshold math from us-data now that policyengine-us 1.689.0 owns the threshold formula.
• Drop legacy spm_unit_spm_threshold inputs from local clone outputs if older source datasets contain them.

Dependency

• Requires policyengine-us>=1.689.0, which includes spm_unit_geographic_adjustment and the updated SPM threshold formula.

Tests

• uv run ruff check policyengine_us_data/utils/spm.py policyengine_us_data/calibration/calibration_utils.py policyengine_us_data/calibration/entity_clone.py policyengine_us_data/calibration/publish_local_area.py policyengine_us_data/datasets/cps/cps.py policyengine_us_data/datasets/cps/extended_cps.py policyengine_us_data/datasets/cps/small_enhanced_cps.py tests/unit/test_extended_cps.py tests/unit/calibration/test_spm_thresholds.py tests/unit/calibration/test_entity_clone.py tests/integration/test_chunked_matrix_builder.py tests/integration/support/tiny_stage_3.py tests/integration/test_tiny_stage_3_artifacts.py
• uv run pytest tests/unit/calibration/test_spm_thresholds.py tests/unit/test_extended_cps.py tests/unit/calibration/test_entity_clone.py tests/integration/test_tiny_stage_3_artifacts.py tests/integration/test_chunked_matrix_builder.py