Validation checklist (C# vs Python)

Goal: verify output parity for the same ISIN and inputs.

1) Build inputs
   - Use the same ISIN and the same prompts in both apps.
   - Set the same number of simulations.
   - Use the same dividend flag (s/n).
   - Optional: set the same RNG seed in Python.

2) Compare core outputs
   - Correlation matrix and volatility values.
   - Fair value output line (value and date).
   - Percent "Sopra/Sotto" and average gain/loss.
   - Valore atteso.

3) Edge cases
   - Ask = 0 and Bid > 0 (reference price changes to Bid).
   - Ex-date warning when DaysToExDate > DaysToObs and last ExDate > last ObsDate.

Notes
- Monte Carlo output is stochastic; use a seed to reduce variance.
- If parity differs, compare intermediate inputs printed in the tables.