feat: add Scottish Child Payment 2026-27 rate increase

changelog_entry.yaml

@@ -0,0 +1,4 @@
+- bump: minor
+  changes:
+    added:
+      - Scottish Child Payment increased to 28.20/week for 2026-27, per Scottish Budget 2026-27.

policyengine_uk/parameters/gov/social_security_scotland/scottish_child_payment/amount.yaml

@@ -6,6 +6,7 @@ values:
   2022-11-14: 25
   2024-04-01: 26.70
   2025-04-01: 27.15
+  2026-04-01: 28.20
 metadata:
   unit: currency-GBP
   period: week
@@ -15,3 +16,5 @@ metadata:
       href: https://www.legislation.gov.uk/ssi/2020/351/regulation/20
     - title: Scottish Government - Scottish Child Payment
       href: https://www.gov.scot/policies/social-security/scottish-child-payment/
+    - title: Scottish Budget 2026-27
+      href: https://www.gov.scot/news/a-budget-to-tackle-child-poverty/

policyengine_uk/tests/policy/baseline/gov/social_security_scotland/scottish_child_payment.yaml

@@ -415,3 +415,27 @@
     # £27.15/week * 52 weeks = £1,411.80
     # [grandparent, child_1]
     scottish_child_payment: [0, 1412]
+
+# 2026-27 rate increase
+
+- name: SCP with 2026 amount (28.20/week)
+  period: 2026
+  absolute_error_margin: 10
+  input:
+    people:
+      parent:
+        age: 30
+      child_1:
+        age: 5
+    benunits:
+      benunit:
+        members: [parent, child_1]
+        universal_credit: 5000
+    households:
+      household:
+        members: [parent, child_1]
+        region: SCOTLAND
+  output:
+    # 28.20/week * 52 weeks = 1,466.40
+    # [parent, child_1]
+    scottish_child_payment: [0, 1466]