feat(cot): add combined (futures+options) COT extractor and transform models

- extract/cftc_cot: refactor extract_cot_year() to accept url_template and
  landing_subdir params; add _extract_cot() shared loop; add extract_cot_combined()
  entry point using com_disagg_txt_{year}.zip → landing/cot_combined/
- pyproject.toml: add extract_cot_combined script entry point
- macros/__init__.py: add @cot_combined_glob() for cot_combined/**/*.csv.gzip
- fct_cot_positioning.sql: union cot_glob and cot_combined_glob in src CTE;
  add report_type column (FutOnly_or_Combined) to cast_and_clean + deduplicated;
  include FutOnly_or_Combined in hkey to avoid key collisions; add report_type to grain
- obt_cot_positioning.sql: add report_type = 'FutOnly' filter to preserve
  existing serving behavior
- obt_cot_positioning_combined.sql: new serving model filtered to report_type =
  'Combined'; identical analytics (COT index, net %, windows) on combined data
- pipelines.py: register extract_cot_combined; add to extract_all meta-pipeline

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

transform/sqlmesh_materia/models/foundation/fct_cot_positioning.sql

@@ -4,7 +4,7 @@ MODEL (
   kind INCREMENTAL_BY_TIME_RANGE (
     time_column report_date
   ),
-  grain (cftc_commodity_code, report_date, cftc_contract_market_code, ingest_date),
+  grain (cftc_commodity_code, report_date, cftc_contract_market_code, ingest_date, report_type),
   start '2006-06-13',
   cron '@daily'
 );
@@ -21,6 +21,18 @@ WITH src AS (
     all_varchar = TRUE,
     max_line_size = 10000000
   )
+  UNION ALL BY NAME
+  SELECT
+    *
+  FROM READ_CSV(
+    @cot_combined_glob(),
+    compression = 'gzip',
+    header = TRUE,
+    union_by_name = TRUE,
+    filename = TRUE,
+    all_varchar = TRUE,
+    max_line_size = 10000000
+  )
 ), cast_and_clean AS (
   SELECT
     TRIM(market_and_exchange_names) AS market_and_exchange_name, /* Identifiers */
@@ -28,6 +40,7 @@ WITH src AS (
     TRIM(cftc_commodity_code) AS cftc_commodity_code,
     TRIM(cftc_contract_market_code) AS cftc_contract_market_code,
     TRIM(contract_units) AS contract_units,
+    TRIM("FutOnly_or_Combined") AS report_type, /* 'FutOnly' or 'Combined' — discriminates the two CFTC report variants */
     TRY_CAST(open_interest_all AS INT) AS open_interest, /* Open interest */ /* CFTC uses '.' as null for any field — use TRY_CAST throughout */
     TRY_CAST(prod_merc_positions_long_all AS INT) AS prod_merc_long, /* Producer / Merchant (commercial hedgers: exporters, processors) */
     TRY_CAST(prod_merc_positions_short_all AS INT) AS prod_merc_short,
@@ -66,12 +79,13 @@ WITH src AS (
       cftc_commodity_code,
       report_date_as_yyyy_mm_dd,
       cftc_contract_market_code,
+      "FutOnly_or_Combined",
       open_interest_all,
       m_money_positions_long_all,
       m_money_positions_short_all,
       prod_merc_positions_long_all,
       prod_merc_positions_short_all
-    ) AS hkey /* Dedup key: hash of business grain + key metrics */
+    ) AS hkey /* Dedup key: hash of business grain + key metrics; includes report variant so fut-only and combined rows get distinct keys */
   FROM src
   /* Reject rows with null commodity code or malformed date */
   WHERE
@@ -119,6 +133,7 @@ WITH src AS (
     ANY_VALUE(traders_managed_money_short) AS traders_managed_money_short,
     ANY_VALUE(traders_managed_money_spread) AS traders_managed_money_spread,
     ANY_VALUE(ingest_date) AS ingest_date,
+    ANY_VALUE(report_type) AS report_type,
     hkey
   FROM cast_and_clean
   GROUP BY