Add ORG labor-market imputations to CPS and eCPS

[MaxGhenis]

Summary

Fixes #587.

This adds ORG-derived labor-market inputs to policyengine-us-data:

• imputes hourly_wage, is_paid_hourly, and is_union_member_or_covered onto CPS persons
• carries those variables through source imputation and Extended CPS stage 2
• uses primary 2024 Census Basic Monthly CPS outgoing-rotation-group records for wage/hourly-status inputs
• assigns union coverage from official 2024 BLS union-representation tables with state-level targeting and demographic weighting

Why

The pre-ORG eCPS was effectively missing hourly-pay status, which feeds the overtime eligibility path in policyengine-us. Adding ORG materially improves the estimated overtime tax expenditure on the published eCPS weights.

Using the same published enhanced_cps_2024.h5 before and after ORG overlay:

• 2026 overtime deduction tax expenditure rises from $9.63B to $14.56B
• that is +$4.93B or +51.2%

Caveat: that comparison is on the published eCPS weights with ORG overlaid, not a fully regenerated Enhanced CPS artifact.

Validation

• 49 tests passed across ORG, source imputation, and Extended CPS
• full-year donor cache summary looked reasonable: 119,237 donor rows, weighted mean hourly wage $35.17, paid-hourly share 55.3%, union coverage 11.0%
• validation notebook gist: https://gist.github.com/MaxGhenis/634977ffccb65a288f54d602a2244ed9

Companion PR

• policyengine-us: adds downstream input variables for hourly_wage and is_union_member_or_covered
  Add ORG-backed hourly wage and union inputs policyengine-us#7909

[MaxGhenis]

Closing in favor of #674, which is opened from an upstream branch so CI can run.