Add Indiana M.E.D. Works (Medicaid buy-in for workers with disabilities)

## Program

Indiana M.E.D. Works (Medicaid for Employees with Disabilities) — Indiana's Medicaid buy-in for workers with disabilities under the Ticket to Work basic coverage group.

## Current state

`is_working_disabled_buy_in_for_medicaid` models three state buy-in programs (California 250% WDP, Illinois HBWD, Mississippi Working Disabled). Indiana is not among them, so working Hoosiers with disabilities above the 138% FPL adult-expansion line are modeled as having no Medicaid pathway even when M.E.D. Works would cover them.

## Rules (IN FSSA)

- Disabled and working
- Countable income above 100% and at or below 350% FPL
- Asset limit $2,000 single / $3,000 couple (applicant's assets only)
- Sliding-scale premiums

Sources:
- Program page: https://www.in.gov/fssa/ompp/med-works/
- Fact sheet (100–350% FPL, $2,000/$3,000 assets): https://www.in.gov/fssa/ompp/files/MEDWorksFactsSheet.pdf

## Suggested implementation

Add `in_med_works_eligible` (person-level, monthly like the IL/MS variables) and OR it into `is_working_disabled_buy_in_for_medicaid`, with parameters under `gov/states/in/fssa/med_works/`.

## Context

Surfaced while triaging PolicyBench reference values (PolicyEngine/policybench#91, scenario_015): a disabled worker at 268.9% FPL in IN. That specific household would still be ineligible ($584,850 countable assets ≫ $2,000), so this gap did not produce a wrong reference — it is an enhancement, not a bug.

Start by reading is_working_disabled_buy_in_for_medicaid and the existing person-level Illinois and Mississippi variables. Add the Indiana implementation under gov/states/in/fssa/med_works/ using the stated income, asset, disability, work, and premium rules, then include it in the existing buy-in condition. Done means eligible Indiana workers with disabilities can qualify through M.E.D. Works while the documented asset limits are applied.

Written by the indexing model from the issue text.