Function cmd_models_exercise 

pub async fn cmd_models_exercise(
    base_url: &str,
    model: &str,
    iterations: usize,
) -> Result<(), Box<dyn Error>>

Exercise a model across the task class matrix (5 complexity x 4 intent) to populate per-(model, intent_class) quality observations.

iterations controls how many full matrix passes to run. Each pass is 20 prompts. Use iterations=20 for 100 observations per intent class.