Function validate_square_root_law 

pub fn validate_square_root_law(
    demand_std_1: f64,
    safety_stock_1: f64,
    demand_std_2: f64,
    safety_stock_2: f64,
    tolerance: f64,
) -> Result<TpsTestResult, String>

Validates Square Root Law for safety stock.

TC-9: Safety stock scales as √demand, not linearly

Errors

This function always returns Ok. The Result type is for consistency.