SDLT schedules miss the 5% additional-dwellings surcharge (31 Oct 2024) and the 2022-25 thresholds #2245

What happens

The SDLT residential schedules on main (e89b8ab) miss two changes:

1. Higher rates for additional dwellings. stamp_duty/residential/purchase/additional/rate.yaml keeps the 3% surcharge scale (3/5/8/13/15%). The surcharge rose to 5% for transactions with an effective date on or after 31 October 2024, giving 5/7/10/15/17%. The scorecard replay notes this too (Add certified-bundle replay pipeline for recent OBR fiscal events policyengine-scorecard#157, MODEL_INVESTIGATIONS.md).
2. The 23 September 2022 to 31 March 2025 thresholds. The residential nil-rate band was £250,000, and first-time buyers' relief ran to £425,000 on prices up to £625,000, returning to £125,000, £300,000 and £500,000 from 1 April 2025. main/subsequent.yaml, main/first/*.yaml and the additional-dwellings scale have no values for that period. Government guidance: https://www.gov.uk/government/publications/stamp-duty-land-tax-temporary-reductions-for-residential-properties/stamp-duty-land-tax-temporary-increase-to-thresholds

The 2021 holiday dates also look off: the nil band was £500,000 to 30 June 2021 and £250,000 to 30 September 2021, but the scale returns to £125,000 on 2021-03-31.

Fix

Date every band to its legislation (Finance Act 2003 s. 55 and Sch. 4ZA as amended, and the 2020-2022 temporary relief and reduction Acts) and add YAML tests at each change date. Fiscal-year conversion samples 30 April, so FY2024 should use the £250,000 band and FY2025 the 5% surcharge.

Found while fixing #2238 (#2241).