Add legislative references to PAWHP parameter suite (#1458) (#1702)

#1458 asks for legislative references on every policy parameter. This is a
down-payment focused on the Pension Age Winter Heating Payment (Scotland)
suite, where none of the six YAML files carried a statutory reference and
two of the labels were copy-paste leftovers from Winter Fuel Payment.

- amount/{lower,higher,base}: add proper descriptions, fix the labels
  ("PAWHP lower (under-80) amount", etc., instead of three files all
  labelled "Pawhp lower amount") and cite SSI 2024/250 plus the June 2025
  Scottish Government announcement reinstating a universal element for
  winter 2025-26.
- eligibility/{state_pension_age_requirement,higher_age_requirement,
  require_benefits}: cite the relevant regs of SSI 2024/250.

No simulation-visible value changes; just metadata.

Author: vahid-ahmadi

changelog.d/1458-pawhp-refs.md

@@ -0,0 +1 @@
+- Add legislative references and tidy labels for the Pension Age Winter Heating Payment (Scotland) parameter suite (amounts and eligibility), citing The Pension Age Winter Heating Payment (Scotland) Regulations 2024 (SSI 2024/250) and the June 2025 Scottish Government announcement reinstating a universal element.

policyengine_uk/parameters/gov/social_security_scotland/pawhp/amount/base.yaml

@@ -1,8 +1,15 @@
-description: Amount paid to non-benefit-claiming pensioners for the PAWHP.
+description: Pension Age Winter Heating Payment universal base award paid to Scottish State-Pension-age households that do not qualify for a means-tested PAWHP. £0 in winter 2024-25 (PAWHP was means-tested only); £100 from winter 2025-26 following the Scottish Government's reinstatement of a universal element.
 values:
   2024-01-01: 0
   2025-01-01: 100
 metadata:
   unit: currency-GBP
-  label: Pawhp base payment
+  label: PAWHP universal base amount
   uprating: gov.economic_assumptions.indices.obr.consumer_price_index
+  reference:
+    - title: The Pension Age Winter Heating Payment (Scotland) Regulations 2024 (SSI 2024/250)
+      href: https://www.legislation.gov.uk/ssi/2024/250/contents/made
+    - title: Scottish Government — Pension Age Winter Heating Payment to be paid to all pensioners (June 2025)
+      href: https://www.gov.scot/news/winter-fuel-payment-to-be-paid-to-all-pensioners/
+    - title: Social Security Scotland — Pension Age Winter Heating Payment
+      href: https://www.mygov.scot/pension-age-winter-heating-payment

policyengine_uk/parameters/gov/social_security_scotland/pawhp/amount/higher.yaml

@@ -1,6 +1,12 @@
+description: Pension Age Winter Heating Payment higher (80-and-over) award paid to Scottish households containing someone aged 80 or over who receives a qualifying benefit.
 values:
   2024-01-01: 300
 metadata:
   unit: currency-GBP
-  label: Pawhp lower amount
+  label: PAWHP higher (80+) amount
   uprating: gov.economic_assumptions.indices.obr.consumer_price_index
+  reference:
+    - title: The Pension Age Winter Heating Payment (Scotland) Regulations 2024 (SSI 2024/250)
+      href: https://www.legislation.gov.uk/ssi/2024/250/contents/made
+    - title: Social Security Scotland — Pension Age Winter Heating Payment
+      href: https://www.mygov.scot/pension-age-winter-heating-payment

policyengine_uk/parameters/gov/social_security_scotland/pawhp/amount/lower.yaml

@@ -1,6 +1,12 @@
+description: Pension Age Winter Heating Payment lower (under-80) award paid to Scottish households containing someone of State Pension age who receives a qualifying benefit.
 values:
   2024-01-01: 200
 metadata:
   unit: currency-GBP
-  label: Pawhp lower amount
-  uprating: gov.economic_assumptions.indices.obr.consumer_price_index
+  label: PAWHP lower (under-80) amount
+  uprating: gov.economic_assumptions.indices.obr.consumer_price_index
+  reference:
+    - title: The Pension Age Winter Heating Payment (Scotland) Regulations 2024 (SSI 2024/250)
+      href: https://www.legislation.gov.uk/ssi/2024/250/contents/made
+    - title: Social Security Scotland — Pension Age Winter Heating Payment
+      href: https://www.mygov.scot/pension-age-winter-heating-payment

policyengine_uk/parameters/gov/social_security_scotland/pawhp/eligibility/higher_age_requirement.yaml

@@ -1,6 +1,9 @@
-description: Age requirement to qualify for the higher PAWHP.
+description: Age at which a qualifying household becomes entitled to the higher PAWHP award.
 values:
   2000-01-01: 80
 metadata:
   unit: year
-  label: Winter Fuel Payment higher amount age requirement
+  label: PAWHP higher amount age requirement
+  reference:
+    - title: The Pension Age Winter Heating Payment (Scotland) Regulations 2024 (SSI 2024/250), reg. 5
+      href: https://www.legislation.gov.uk/ssi/2024/250/regulation/5/made

policyengine_uk/parameters/gov/social_security_scotland/pawhp/eligibility/require_benefits.yaml

@@ -1,8 +1,16 @@
-description: Whether receipt of means-tested benefits is required to qualify for the Winter Fuel Payment.
+description: Whether receipt of a qualifying means-tested benefit is required for PAWHP entitlement.
 values:
   2000-01-01: false
-  2024-01-01: 
+  2024-01-01:
     value: true
+    reference:
+      - title: The Pension Age Winter Heating Payment (Scotland) Regulations 2024 (SSI 2024/250), reg. 4
+        href: https://www.legislation.gov.uk/ssi/2024/250/regulation/4/made
 metadata:
   unit: bool
-  label: Pawhp means-tested benefits requirement
+  label: PAWHP means-tested benefits requirement
+  reference:
+    - title: The Pension Age Winter Heating Payment (Scotland) Regulations 2024 (SSI 2024/250)
+      href: https://www.legislation.gov.uk/ssi/2024/250/contents/made
+    - title: Scottish Government — Pension Age Winter Heating Payment to be paid to all pensioners (June 2025)
+      href: https://www.gov.scot/news/winter-fuel-payment-to-be-paid-to-all-pensioners/

policyengine_uk/parameters/gov/social_security_scotland/pawhp/eligibility/state_pension_age_requirement.yaml

@@ -1,6 +1,9 @@
-description: Whether individuals must be State Pension Age to qualify for the PAWHP.
+description: Whether individuals must be of State Pension Age to qualify for the PAWHP.
 values:
   2000-01-01: true
 metadata:
   unit: bool
-  label: Pawhp State Pension age requirement
+  label: PAWHP State Pension age requirement
+  reference:
+    - title: The Pension Age Winter Heating Payment (Scotland) Regulations 2024 (SSI 2024/250), reg. 3
+      href: https://www.legislation.gov.uk/ssi/2024/250/regulation/3/made