Add Texas CEAP (LIHEAP)

[MaxGhenis]

Summary

• Implements Texas Comprehensive Energy Assistance Program (CEAP), the state's LIHEAP program administered by TDHCA
• Income eligibility uses the higher of 150% FPG or 60% state median income (per FY 2024 LIHEAP State Plan, Section 2.1)
• Tiered utility assistance benefits per 10 TAC 6.309(e): $2,400 (0-50% FPIG), $2,300 (51-75% FPIG), $2,200 (76-150% FPIG), capped by actual energy expenses

Test plan

• 4 eligibility tests (TX eligible, TX ineligible above both limits, zero income, non-TX state)
• 5 benefit amount tests (low/mid/high income brackets, expense cap, ineligible household)
• All 9 YAML tests pass via policyengine-core test

Fixes #6465

Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (55a0045) to head (07d81a5).
⚠️ Report is 20 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #7516      +/-   ##
===========================================
+ Coverage   97.82%   100.00%   +2.17%     
===========================================
  Files           3         2       -1     
  Lines          92        35      -57     
  Branches        2         0       -2     
===========================================
- Hits           90        35      -55     
+ Misses          1         0       -1     
+ Partials        1         0       -1     

Flag	Coverage Δ
unittests	100.00% <100.00%> (+2.17%)	⬆️

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