Address remaining review findings from #9345

[DTrim99]

Summary

Of the 9 review findings on #9345, 8 were resolved before that PR merged. This follow-up applies the 3 that remained:

1. Anchored SNAP student regulatory citations — is_snap_ineligible_student now cites 7 CFR 273.7(b)(1)(ii) and 273.24(c)(2)(i) with deep-link anchors (#b_1_ii, #c_2_i) alongside the existing reference. Formula untouched.
2. SSI working student exclusion eligibility variable — removed a stray unit = USD and corrected value_type from float to bool on is_ssi_blind_or_disabled_working_student_exclusion_eligible (a boolean eligibility variable used only as defined_for).
3. Month-aggregation test for is_usda_disabled — added a case with a month-keyed receives_ssi input evaluated over a year period, verifying monthly SSI aggregation.

Tests

102/102 passing across the three affected suites:

• is_usda_disabled.yaml: 9/9 (incl. new case)
• SSI working student exclusion: 14/14
• snap/eligibility/student/: 79/79

🤖 Generated with Claude Code

https://claude.ai/code/session_01LqCGPgxDukji8Bhs57c5rH

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.88%. Comparing base (f9b5549) to head (e3407dd).
⚠️ Report is 55 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##              main    #9433       +/-   ##
============================================
- Coverage   100.00%   88.88%   -11.12%     
============================================
  Files            2        2               
  Lines           20       27        +7     
============================================
+ Hits            20       24        +4     
- Misses           0        3        +3     

Flag	Coverage Δ
unittests	88.88% <100.00%> (-11.12%)	⬇️

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[DTrim99]

Closing — this follow-up targeted the wrong PR number; the intended review target is a different PR.