feat(pipeline): dim_school/dim_location store GIAS codes; seed drift test

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

pipeline/transform/tests/assert_gias_code_names_match_seed.sql

@@ -0,0 +1,33 @@
+-- Warn when the live GIAS CSV carries a (code, name) pair we don't have in
+-- the dictionary seed — i.e. DfE added or renamed a value. Fix by rerunning
+-- pipeline/scripts/generate_gias_codes.py and committing the regenerated
+-- dictionaries + seed together.
+{{ config(severity='warn') }}
+
+with raw_pairs as (
+    {% for field_key, code_col, name_col in [
+        ('school_type',          'TypeOfEstablishment (code)',  'TypeOfEstablishment (name)'),
+        ('establishment_status', 'EstablishmentStatus (code)',  'EstablishmentStatus (name)'),
+        ('phase_of_education',   'PhaseOfEducation (code)',     'PhaseOfEducation (name)'),
+        ('official_sixth_form',  'OfficialSixthForm (code)',    'OfficialSixthForm (name)'),
+        ('religious_character',  'ReligiousCharacter (code)',   'ReligiousCharacter (name)'),
+        ('admissions_policy',    'AdmissionsPolicy (code)',     'AdmissionsPolicy (name)')
+    ] %}
+    select distinct
+        '{{ field_key }}' as field,
+        cast(nullif(trim("{{ code_col }}"), '') as integer) as code,
+        nullif(trim("{{ name_col }}"), '') as name
+    from {{ source('raw', 'gias_establishments') }}
+    where nullif(trim("{{ code_col }}"), '') is not null
+      and nullif(trim("{{ name_col }}"), '') is not null
+    {% if not loop.last %}union all{% endif %}
+    {% endfor %}
+)
+
+select r.*
+from raw_pairs r
+left join {{ ref('gias_code_names') }} s
+    on s.field = r.field
+   and s.code = r.code
+   and s.name = r.name
+where s.field is null