Gate tip deduction on both legacy and split SSTB inputs

[MaxGhenis]

Summary

tip_income_deduction_occupation_requirement_met currently checks only the legacy per-person business_is_sstb flag to apply OBBBA §224's SSTB exclusion:

is_sstb = person("business_is_sstb", period)
return (treasury_tipped_occupation_code > 0) & ~is_sstb

After #7944 split QBI into SSTB and non-SSTB components, a self-employed tipped worker can route their activity through sstb_self_employment_income and leave the legacy flag unset. That path silently bypasses the §224 SSTB exclusion and grants the deduction.

Fix

Treat a person as "in the course of" an SSTB if either the legacy flag is set or sstb_self_employment_income > 0. Behavior for anyone using only the legacy flag is unchanged; anyone using only the new split inputs is now correctly excluded.

TDD

Failing test added first:

- name: SSTB self-employment income blocks tip deduction even without legacy flag
  input:
    sstb_self_employment_income: 50_000
    business_is_sstb: false
    treasury_tipped_occupation_code: 102
    tip_income: 5_000
  output:
    tip_income_deduction_occupation_requirement_met: false
    tip_income_deduction: 0

Reproduced the regression (met = True instead of False), then applied the fix.

Test plan

• New YAML case fails on unmodified main, passes after fix.
• All 13 existing tip-deduction YAML cases still pass.
• make format clean.
• PR CI.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (03faf19) to head (e97d72a).
⚠️ Report is 209 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##              main     #8062    +/-   ##
==========================================
  Coverage   100.00%   100.00%            
==========================================
  Files           16         1    -15     
  Lines          261        14   -247     
==========================================
- Hits           261        14   -247     

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

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