Fix COT pipeline: TRY_CAST nulls, dim_commodity leading zeros, correct CFTC codes

- config.yaml: remove ambiguousorinvalidcolumn linter rule (false positives on read_csv TVFs)
- fct_cot_positioning: use TRY_CAST throughout — CFTC uses '.' as null in many columns
- raw/cot_disaggregated: add columns() declaration for 33 varchar cols
- dim_commodity: switch from SEED to FULL model with SQL VALUES to preserve leading zeros
  Pandas auto-converts '083' → 83 even with varchar column declarations in SEED models
- seeds/dim_commodity.csv: correct cftc_commodity_code from '083731' (contract market code)
  to '083' (3-digit CFTC commodity code); add CSV quoting
- test_cot_foundation.yaml: fix output key name, vars for time range, partial: true,
  and correct cftc_commodity_code to '083'
- analytics.py: COFFEE_CFTC_CODE '083731' → '083' to match actual data

Result: serving.cot_positioning has 685 rows (2013-01-08 to 2026-02-17), 23/23 tests pass.

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

web/src/beanflows/analytics.py

@@ -12,8 +12,8 @@ import duckdb
 # Coffee (Green) commodity code in USDA PSD
 COFFEE_COMMODITY_CODE = 711100
 
-# Coffee C futures commodity code in CFTC COT reports
-COFFEE_CFTC_CODE = "083731"
+# Coffee C futures commodity code in CFTC COT reports (3-digit CFTC commodity code)
+COFFEE_CFTC_CODE = "083"
 
 # Metrics safe for user-facing queries (prevents SQL injection in dynamic column refs)
 ALLOWED_METRICS = frozenset({