Implement Georgia HB463 (2025-2026): tax rate cut + standard deduction / dependent exemption increases + retirement exclusion + overtime/tips exemptions

[DTrim99]

Implement Georgia HB463 (Act of 2026 reducing income tax rates and increasing deductions), which:

In-scope direct changes (no trigger)

• Tax rate (O.C.G.A. § 48-7-20(a.1)): 5.19% → 4.99% for TY 2026
• Standard deduction (O.C.G.A. § 48-7-27(a)(1)(B)): Joint $24K → $30K, Single/HoH/Separate $12K → $15K for TY 2026
• Dependent exemption (O.C.G.A. § 48-7-26(b)): $4,000 → $5,000 per dependent for TY 2026
• Retirement income exclusion (O.C.G.A. § 48-7-27(a)(5)(A)(xiv)): age-65+ cap $65K → $70K for TY 2027+

In-scope new exemptions (TY 2026-2028 only, self-repeals)

• Qualified overtime compensation exemption (O.C.G.A. § 48-7-27(a)(16)): up to $1,750 of overtime (IRC §225) for full-time hourly employees
• Cash tips exemption (O.C.G.A. § 48-7-27(a)(17)): up to $1,750 of cash tips from customarily-tipped occupations

Out of scope (trigger-conditional, will be commented in code)

Bill provides for prospective annual reductions/increases subject to revenue-shortfall-reserve and Governor's-revenue-estimate triggers. Whether these triggers fire in any given year cannot be predicted from the bill alone:

• Future tax-rate cuts of 0.10% per year (target 3.99%)
• Future SD increases of $750 (joint) / $375 (single) per year (targets $36K/$18K)
• Future dependent-exemption increases of $125 per year (target $6K)

These are noted in YAML comments but not modeled with future-dated values.