- Removed CORP_AA_LOGR (log of rate = problematic near zero)
- Rate variables restricted to DIFF only (no LOG/PCT/LOGR)
- Added economic sign consistency checks for all 45 features
- New optimal 3-var: CREDIT_SPREAD_LAG1, IPI_LAG1, EXPORT_DIFF
- All coefficient signs economically consistent
- R²=0.586 (trade-off: lower R² but correct economics)
- Added IPI + EXPORT to ECOS queries and fallback data
- Zt restricted to 2000-2025 in analysis (26 obs)
- Pipeline 8/8 validation pass
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