Apply state-specific Medicaid countable income rules

[daphnehanse11]

Fixes #6175

Summary

• add a Medicaid-specific countable income variable for the optional senior or disabled pathway instead of reusing ssi_countable_income
• apply each state's Medicaid disregard within the SSI-style income calculation and add a Connecticut override for its unearned-income-specific rule
• refresh Connecticut's 2023-2025 disregard and income-limit parameters and add coverage for earned, unearned, and joint-filer tests

Testing

• uv run policyengine-core test -c policyengine_us policyengine_us/tests/policy/baseline/gov/hhs/medicaid/income/medicaid_optional_senior_or_disabled_countable_income.yaml policyengine_us/tests/policy/baseline/gov/hhs/medicaid/eligibility/categories/is_optional_senior_or_disabled_income_eligible.yaml
• uv run policyengine-core test -c policyengine_us policyengine_us/tests/policy/baseline/gov/hhs/medicaid policyengine_us/tests/policy/baseline/gov/ssa/ssi

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (f9a4a0f) to head (7806f2d).
⚠️ Report is 1161 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main     #8167   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
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  Files            7         6    -1     
  Lines          215       121   -94     
  Branches         6         0    -6     
=========================================
- Hits           215       121   -94     

Flag	Coverage Δ
unittests	100.00% <100.00%> (ø)

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[daphnehanse11]

Reviewed the PR diff before making any edits. I checked the Medicaid-specific countable income flow against the branch’s SSI-style exclusion/deeming patterns, the Connecticut unearned-income disregard override, joint-filer aggregation, parameter metadata, test coverage, and period handling.

I do not see a behavioral blocker in the PR diff against its base. One metadata issue should be patched: the added Connecticut PDF references do not include page anchors, making the new parameter values harder to audit. I verified the relevant source pages locally: the 2023 and 2024 HUSKY C values are on PDF page 2, and the 2025 values are on PDF page 1.

I’m patching that from a fresh detached /tmp worktree based on origin/codex/issue-6175-medicaid-income, then I’ll run the narrow Medicaid/SSI tests for the changed files.