EWMA Portfolio Risk Decomposition — Debug and Fix

EWMA Portfolio Risk Decomposition — Debug and Fix: a task in skilltrainbench-public: skilltrainbench training tasks (Harbor dataset). A colleague wrote a Python script ( /app/data/template.py ) to compute EWMA covariance, parametric VaR, and Euler risk decomposition for a 5-asset ETF portfolio…

The task

A colleague wrote a Python script (`/app/data/template.py`) to compute EWMA covariance, parametric VaR, and Euler risk decomposition for a 5-asset ETF portfolio. The script runs but **produces incorrect results** — some outputs are numerically wrong due to implementation errors.

Part of codeslord/skilltrainbench-public.