feat(extract): convert geonames to JSONL output

- cities_global.jsonl.gz replaces .json.gz (one city object per line)
- Empty placeholder writes a minimal .jsonl.gz (null row, filtered in staging)
- Eliminates the {"rows": [...]} blob wrapper and maximum_object_size workaround

stg_population_geonames: UNION ALL transition (jsonl_rows + blob_rows)
  - jsonl_rows: read_json JSONL, explicit columns, no UNNEST
  - blob_rows: existing UNNEST(rows) pattern with 40MB size limit retained

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

transform/sqlmesh_padelnomics/models/staging/stg_population_geonames.sql

@@ -3,7 +3,11 @@
 -- Broad coverage (140K+ locations) enables Gemeinde-level market intelligence.
 -- One row per geoname_id (GeoNames stable numeric identifier).
 --
--- Source: data/landing/geonames/{year}/{month}/cities_global.json.gz
+-- Supports two landing formats (UNION ALL during migration):
+--   New: cities_global.jsonl.gz — one city per line, columns directly accessible
+--   Old: cities_global.json.gz  — {"rows": [...]} blob (UNNEST required)
+--
+-- Source: data/landing/geonames/{year}/{month}/cities_global.{jsonl,json}.gz
 
 MODEL (
   name staging.stg_population_geonames,
@@ -12,7 +16,33 @@ MODEL (
   grain geoname_id
 );
 
-WITH parsed AS (
+WITH
+-- New format: one city per JSONL line
+jsonl_rows AS (
+  SELECT
+    TRY_CAST(geoname_id  AS INTEGER)  AS geoname_id,
+    city_name,
+    country_code,
+    TRY_CAST(lat         AS DOUBLE)   AS lat,
+    TRY_CAST(lon         AS DOUBLE)   AS lon,
+    admin1_code,
+    admin2_code,
+    TRY_CAST(population  AS BIGINT)   AS population,
+    TRY_CAST(ref_year    AS INTEGER)  AS ref_year,
+    CURRENT_DATE                      AS extracted_date
+  FROM read_json(
+    @LANDING_DIR || '/geonames/*/*/cities_global.jsonl.gz',
+    format = 'newline_delimited',
+    columns = {
+      geoname_id: 'INTEGER', city_name: 'VARCHAR', country_code: 'VARCHAR',
+      lat: 'DOUBLE', lon: 'DOUBLE', admin1_code: 'VARCHAR', admin2_code: 'VARCHAR',
+      population: 'BIGINT', ref_year: 'INTEGER'
+    }
+  )
+  WHERE geoname_id IS NOT NULL
+),
+-- Old format: {"rows": [...]} blob — kept for transition
+blob_rows AS (
   SELECT
     TRY_CAST(row ->> 'geoname_id'  AS INTEGER)  AS geoname_id,
     row ->> 'city_name'                          AS city_name,
@@ -33,11 +63,16 @@ WITH parsed AS (
     )
   )
   WHERE (row ->> 'geoname_id') IS NOT NULL
+),
+all_rows AS (
+  SELECT * FROM jsonl_rows
+  UNION ALL
+  SELECT * FROM blob_rows
 )
 SELECT
   geoname_id,
-  TRIM(city_name)      AS city_name,
-  UPPER(country_code)  AS country_code,
+  TRIM(city_name)                AS city_name,
+  UPPER(country_code)            AS country_code,
   lat,
   lon,
   NULLIF(TRIM(admin1_code), '')  AS admin1_code,
@@ -45,7 +80,7 @@ SELECT
   population,
   ref_year,
   extracted_date
-FROM parsed
+FROM all_rows
 WHERE population IS NOT NULL
   AND population > 0
   AND geoname_id IS NOT NULL