fix(pipeline): expand GIAS schema, handle empty strings, scope DAG selectors

- Declare all 34 columns needed by dbt in GIAS tap schema (target-postgres
  only persists columns present in the Singer schema message)
- Use nullif() for empty-string-to-integer/date casts in staging models
- Scope daily DAG dbt build to GIAS models only (stg_gias_establishments+
  stg_gias_links+) to avoid errors on unloaded sources
- Scope annual EES DAG similarly; remove redundant dbt test steps
- Make dim_school gracefully handle missing int_ofsted_latest table

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

pipeline/transform/models/marts/dim_school.sql

@@ -2,12 +2,14 @@
 
 with schools as (
     select * from {{ ref('stg_gias_establishments') }}
-),
-
-latest_ofsted as (
-    select * from {{ ref('int_ofsted_latest') }}
 )
 
+{% set ofsted_relation = adapter.get_relation(
+    database=target.database,
+    schema=target.schema,
+    identifier='int_ofsted_latest'
+) %}
+
 select
     s.urn,
     s.local_authority_code * 1000 + s.establishment_number as laestab,
@@ -30,11 +32,19 @@ select
     s.nursery_provision,
     s.admissions_policy,
 
-    -- Latest Ofsted
+    -- Latest Ofsted (populated after monthly Ofsted pipeline runs)
+    {% if ofsted_relation is not none %}
     o.overall_effectiveness as ofsted_grade,
     o.inspection_date as ofsted_date,
     o.framework as ofsted_framework
+    {% else %}
+    null::text as ofsted_grade,
+    null::date as ofsted_date,
+    null::text as ofsted_framework
+    {% endif %}
 
 from schools s
-left join latest_ofsted o on s.urn = o.urn
+{% if ofsted_relation is not none %}
+left join {{ ref('int_ofsted_latest') }} o on s.urn = o.urn
+{% endif %}
 where s.status = 'Open'

pipeline/transform/models/staging/stg_gias_establishments.sql

@@ -8,9 +8,9 @@ with source as (
 renamed as (
     select
         cast("URN" as integer)                          as urn,
-        cast("LA (code)" as integer)                    as local_authority_code,
+        cast(nullif("LA (code)", '') as integer)        as local_authority_code,
         "LA (name)"                                     as local_authority_name,
-        cast("EstablishmentNumber" as integer)          as establishment_number,
+        cast(nullif("EstablishmentNumber", '') as integer) as establishment_number,
         "EstablishmentName"                             as school_name,
         "TypeOfEstablishment (name)"                    as school_type,
         "PhaseOfEducation (name)"                       as phase,
@@ -18,7 +18,7 @@ renamed as (
         "ReligiousCharacter (name)"                     as religious_character,
         "AdmissionsPolicy (name)"                       as admissions_policy,
         "SchoolCapacity"                                as capacity,
-        cast("NumberOfPupils" as integer)               as total_pupils,
+        cast(nullif("NumberOfPupils", '') as integer)   as total_pupils,
         "HeadTitle (name)"                              as head_title,
         "HeadFirstName"                                 as head_first_name,
         "HeadLastName"                                  as head_last_name,
@@ -30,18 +30,17 @@ renamed as (
         "County (name)"                                 as county,
         "Postcode"                                      as postcode,
         "EstablishmentStatus (name)"                    as status,
-        cast("OpenDate" as date)                        as open_date,
-        cast("CloseDate" as date)                       as close_date,
+        case when "OpenDate" = '' then null else cast("OpenDate" as date) end   as open_date,
+        case when "CloseDate" = '' then null else cast("CloseDate" as date) end as close_date,
         "Trusts (name)"                                 as academy_trust_name,
-        cast("Trusts (code)" as integer)                as academy_trust_uid,
+        cast(nullif("Trusts (code)", '') as integer)    as academy_trust_uid,
         "UrbanRural (name)"                             as urban_rural,
         "ParliamentaryConstituency (name)"              as parliamentary_constituency,
         "NurseryProvision (name)"                       as nursery_provision,
-        cast("Easting" as integer)                      as easting,
-        cast("Northing" as integer)                     as northing,
-        -- Age range
-        cast("StatutoryLowAge" as integer)              as statutory_low_age,
-        cast("StatutoryHighAge" as integer)             as statutory_high_age
+        cast(nullif("Easting", '') as integer)          as easting,
+        cast(nullif("Northing", '') as integer)         as northing,
+        cast(nullif("StatutoryLowAge", '') as integer)  as statutory_low_age,
+        cast(nullif("StatutoryHighAge", '') as integer) as statutory_high_age
     from source
     where "URN" is not null
 )

pipeline/transform/models/staging/stg_gias_links.sql

@@ -9,7 +9,7 @@ renamed as (
         cast("URN" as integer)              as urn,
         cast("LinkURN" as integer)          as linked_urn,
         "LinkType"                          as link_type,
-        cast("LinkEstablishedDate" as date) as link_date
+        case when "LinkEstablishedDate" = '' then null else cast("LinkEstablishedDate" as date) end as link_date
     from source
     where "URN" is not null
       and "LinkURN" is not null