feat(pipeline): Progress 8 banding and KS4 disadvantage gaps in marts

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0146VHeLAWjDVE2B5uU67jCB

pipeline/transform/models/marts/_marts_schema.yml

@@ -104,6 +104,14 @@ models:
         tests: [not_null]
       - name: year
         tests: [not_null]
+      - name: progress_8_banding
+        tests:
+          - accepted_values:
+              values: ['Well above average', 'Above average', 'Average', 'Below average', 'Well below average']
+              config:
+                where: "progress_8_banding is not null"
+      - name: attainment_8_disadvantage_gap
+      - name: progress_8_disadvantage_gap
     tests:
       - unique:
           column_name: "urn || '-' || year"

pipeline/transform/models/marts/fact_ks4_performance.sql

@@ -16,6 +16,9 @@ select
     progress_8_score,
     progress_8_lower_ci,
     progress_8_upper_ci,
+    progress_8_banding,
+    attainment_8_disadvantage_gap,
+    progress_8_disadvantage_gap,
     progress_8_english,
     progress_8_maths,
     progress_8_ebacc,