Add New York STAR property tax relief (focus on Enhanced STAR)

## Summary

Add New York STAR property tax relief, with particular attention to the senior-targeted Enhanced STAR component.

This is a major gap in senior property tax relief coverage. `policyengine-us` already models New York's real property tax credit, but STAR itself does not appear to be modeled.

## Why this matters

- STAR is one of New York's flagship homeowner property tax relief programs.
- Enhanced STAR is explicitly senior-targeted.
- The benefit structure is still part of current law, even though new applicants generally receive the credit instead of the exemption.

## Current official program notes

- New York's STAR program offers property tax relief through either:
- a STAR credit, or
- an existing STAR exemption for legacy recipients
- Enhanced STAR provides a larger benefit for senior citizens age 65 and older with qualifying incomes.
- The benefit applies to school property taxes rather than general state income tax liability.

## Suggested implementation scope

Start with an issue to scope data feasibility before full implementation.

Suggested phases:

1. Determine whether current PolicyEngine inputs can support STAR benefit estimation
2. Decide whether to model:
- Enhanced STAR only, or
- both Basic and Enhanced STAR
3. Determine whether geography-specific school tax / assessed value inputs are sufficient

## Likely complexity

This is probably the hardest of the current property-tax gaps because STAR depends on school-tax relief mechanics, not just a straightforward age-income-rent-property-tax formula.

## Existing PolicyEngine patterns to reuse

- NY real property tax credit:
`policyengine_us/variables/gov/states/ny/tax/income/credits/ny_real_property_tax_credit.py`

## Sources

- New York STAR resource center:
https://www.tax.ny.gov/star/
- New York Types of STAR:
https://www.tax.ny.gov/pit/property/star/types.htm
- New York STAR exemption program:
https://www.tax.ny.gov/pit/property/star/star-exemption-program.htm
- New York register / update STAR:
https://www.tax.ny.gov/pit/property/star/

## Notes

This came up while cross-referencing Lincoln Institute residential property tax relief program data against current `policyengine-us` coverage.