Function validate_shojinka 

pub fn validate_shojinka(
    specialist_throughput: f64,
    specialist_utilization: f64,
    specialist_wait_time: f64,
    flexible_throughput: f64,
    flexible_utilization: f64,
    flexible_wait_time: f64,
    tolerance: f64,
) -> Result<TpsTestResult, String>

Validates Shojinka (Cross-Training) effects.

TC-6: Cross-trained workers outperform specialists under variability

Pooling Effect: When workers can move between stations, the pooled capacity handles variability better than dedicated specialists.

Errors

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