Populate SPM subsidies and drop resource aggregates

[MaxGhenis]

Summary

• Populate CPS SPM capped housing subsidy and energy subsidy under the canonical PolicyEngine concepts.
• Stop bringing Census SPM resource aggregates (SPM_TOTVAL, SPM_RESOURCES) into generated pipeline datasets or clone QRF imputation.
• Keep clone diagnostics based on modeled SPM poverty rather than comparing against imputed reported SPM resources.
• Add guards so generated/uploaded datasets reject the Census SPM resource aggregate variables.

Contract

This builds on #974, which now fail-closes exported computed policyengine-us variables. Formula/adds/subtracts variables can still be temporary construction targets if a stage explicitly deconstructs or renames them to leaf inputs before export.

SPM_TOTVAL and SPM_RESOURCES are different: they are Census SPM output/control aggregates, not leaf inputs and not decomposable into PolicyEngine input variables in this pipeline. They should be used for validation or raw-CPS replication diagnostics only, not exported or imputed into ECPS.

Validation

• uv run ruff format --check policyengine_us_data/datasets/cps/cps.py policyengine_us_data/datasets/cps/extended_cps.py policyengine_us_data/datasets/cps/enhanced_cps.py policyengine_us_data/calibration/formulaic_inputs.py policyengine_us_data/storage/upload_completed_datasets.py tests/integration/support/tiny_stage_3.py tests/integration/support/tiny_stage_4.py tests/integration/support/tiny_stage_5.py tests/integration/test_cps_generation.py tests/integration/test_tiny_stage_3_artifacts.py tests/integration/test_tiny_stage_4_artifacts.py tests/unit/test_enhanced_cps_clone_diagnostics.py tests/unit/test_upload_completed_datasets.py tests/unit/test_extended_cps.py
• uv run ruff check policyengine_us_data/datasets/cps/cps.py policyengine_us_data/datasets/cps/extended_cps.py policyengine_us_data/datasets/cps/enhanced_cps.py policyengine_us_data/calibration/formulaic_inputs.py policyengine_us_data/storage/upload_completed_datasets.py tests/integration/support/tiny_stage_3.py tests/integration/support/tiny_stage_4.py tests/integration/support/tiny_stage_5.py tests/integration/test_cps_generation.py tests/integration/test_tiny_stage_3_artifacts.py tests/integration/test_tiny_stage_4_artifacts.py tests/unit/test_enhanced_cps_clone_diagnostics.py tests/unit/test_upload_completed_datasets.py tests/unit/test_extended_cps.py
• uv run pytest tests/unit/test_extended_cps.py tests/unit/test_enhanced_cps_clone_diagnostics.py tests/unit/test_upload_completed_datasets.py tests/integration/test_cps_generation.py tests/integration/test_tiny_stage_3_artifacts.py tests/integration/test_tiny_stage_4_artifacts.py -q (95 passed)