Add CFTC COT data integration with foundation data model layer

- New extraction package (cftc_cot): downloads yearly Disaggregated Futures ZIPs
  from CFTC, etag-based dedup, dynamic inner filename discovery, gzip normalization
- SQLMesh 3-layer architecture: raw (technical) → foundation (business model) → serving (mart)
- dim_commodity seed: conformed dimension mapping USDA ↔ CFTC codes — the commodity ontology
- fct_cot_positioning: typed, deduplicated weekly positioning facts for all commodities
- obt_cot_positioning: Coffee C mart with COT Index (26w/52w), WoW delta, OI ratios
- Analytics functions + REST API endpoints: /commodities/<code>/positioning[/latest]
- Dashboard widget: Managed Money net, COT Index card, dual-axis Chart.js chart
- 23 passing tests (10 unit + 2 SQLMesh model + existing regression suite)

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

transform/sqlmesh_materia/models/raw/cot_disaggregated.sql

@@ -0,0 +1,85 @@
+-- Raw CFTC Commitment of Traders — Disaggregated Futures Only.
+--
+-- Technical ingestion layer only: reads gzip CSVs from the landing directory
+-- and surfaces the columns needed by downstream foundation models.
+-- All values are varchar; casting happens in foundation.
+--
+-- Source: CFTC yearly ZIPs at
+--   https://www.cftc.gov/files/dea/history/fut_disagg_txt_{year}.zip
+-- Coverage: June 2006 – present (new file every Friday at 3:30 PM ET)
+
+MODEL (
+  name raw.cot_disaggregated,
+  kind FULL,
+  grain (cftc_commodity_code, report_date_as_yyyy_mm_dd, cftc_contract_market_code),
+  start '2006-06-13',
+  cron '@daily'
+);
+
+SELECT
+  -- Identifiers
+  "Market_and_Exchange_Names"   AS market_and_exchange_names,
+  "Report_Date_as_YYYY-MM-DD"  AS report_date_as_yyyy_mm_dd,
+  "CFTC_Commodity_Code"        AS cftc_commodity_code,
+  "CFTC_Contract_Market_Code"  AS cftc_contract_market_code,
+  "Contract_Units"              AS contract_units,
+
+  -- Open interest
+  "Open_Interest_All"           AS open_interest_all,
+
+  -- Producer / Merchant / Processor / User (commercial hedgers)
+  "Prod_Merc_Positions_Long_All"   AS prod_merc_positions_long_all,
+  "Prod_Merc_Positions_Short_All"  AS prod_merc_positions_short_all,
+
+  -- Swap dealers
+  "Swap_Positions_Long_All"        AS swap_positions_long_all,
+  "Swap__Positions_Short_All"      AS swap_positions_short_all,
+  "Swap__Positions_Spread_All"     AS swap_positions_spread_all,
+
+  -- Managed money (hedge funds, CTAs — key speculative signal)
+  "M_Money_Positions_Long_All"     AS m_money_positions_long_all,
+  "M_Money_Positions_Short_All"    AS m_money_positions_short_all,
+  "M_Money_Positions_Spread_All"   AS m_money_positions_spread_all,
+
+  -- Other reportables
+  "Other_Rept_Positions_Long_All"  AS other_rept_positions_long_all,
+  "Other_Rept_Positions_Short_All" AS other_rept_positions_short_all,
+  "Other_Rept_Positions_Spread_All" AS other_rept_positions_spread_all,
+
+  -- Non-reportable (small speculators)
+  "NonRept_Positions_Long_All"     AS nonrept_positions_long_all,
+  "NonRept_Positions_Short_All"    AS nonrept_positions_short_all,
+
+  -- Week-over-week changes
+  "Change_in_Open_Interest_All"    AS change_in_open_interest_all,
+  "Change_in_M_Money_Long_All"     AS change_in_m_money_long_all,
+  "Change_in_M_Money_Short_All"    AS change_in_m_money_short_all,
+  "Change_in_Prod_Merc_Long_All"   AS change_in_prod_merc_long_all,
+  "Change_in_Prod_Merc_Short_All"  AS change_in_prod_merc_short_all,
+
+  -- Concentration (% of OI held by top 4 and top 8 traders)
+  "Conc_Gross_LE_4_TDR_Long_All"   AS conc_gross_le_4_tdr_long_all,
+  "Conc_Gross_LE_4_TDR_Short_All"  AS conc_gross_le_4_tdr_short_all,
+  "Conc_Gross_LE_8_TDR_Long_All"   AS conc_gross_le_8_tdr_long_all,
+  "Conc_Gross_LE_8_TDR_Short_All"  AS conc_gross_le_8_tdr_short_all,
+
+  -- Trader counts
+  "Traders_Tot_All"                AS traders_tot_all,
+  "Traders_M_Money_Long_All"       AS traders_m_money_long_all,
+  "Traders_M_Money_Short_All"      AS traders_m_money_short_all,
+  "Traders_M_Money_Spread_All"     AS traders_m_money_spread_all,
+
+  -- Lineage
+  filename
+FROM read_csv(
+  @cot_glob(),
+  delim = ',',
+  encoding = 'utf-8',
+  compression = 'gzip',
+  header = true,
+  union_by_name = true,
+  filename = true,
+  all_varchar = true,
+  max_line_size = 10000000,
+  ignore_errors = true
+)