Backdating Texas TANF

[hua7450]

Summary

Fixes #7262

Backdate Texas TANF parameters to provide historical data coverage.

Changes

Static Parameters (unchanged since original dates)

Parameter	New Start Date	Source
Resource limit ($1,000)	2009-09-01	1 Tex. Admin. Code § 372.354
Vehicle exemption ($4,650)	2009-09-01	1 Tex. Admin. Code § 372.354
Budgetary needs (all types)	1994-03-01	Texas Works Handbook C-110
Recognizable needs	1994-03-01	Texas Works Handbook C-110

Payment Standards (annual FPL-based adjustments)

Added values for 2017-10-01, 2018-10-01, 2019-10-01:

Year	Source	Notes
2019-10-01	Bulletin 19-08	Actual values from official bulletin
2017-10-01, 2018-10-01	Estimated	Original bulletins unavailable

Estimation Method (2017-2018)

Per state law, Texas TANF maximum grants are adjusted to 17% of FPL. Values calculated using:

Rate = (17% × monthly FPL for size 3) ÷ budgetary needs for size 3
- 2017: 38.48%
- 2018: 39.15%

Rate applied uniformly to all family types/sizes via budgetary needs.

Test Plan

• Texas TANF tests pass (114 tests)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.52%. Comparing base (849bec6) to head (3e8843a).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##              main    #7266       +/-   ##
============================================
- Coverage   100.00%   73.52%   -26.48%     
============================================
  Files            1     3728     +3727     
  Lines           19    53706    +53687     
  Branches         1      266      +265     
============================================
+ Hits            19    39490    +39471     
- Misses           0    14188    +14188     
- Partials         0       28       +28     

Flag	Coverage Δ
unittests	73.52% <ø> (-26.48%)	⬇️

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