Function calculate_dense_times 

pub fn calculate_dense_times(
    start_time: f64,
    end_time: f64,
    obs_times: &[f64],
    idelta: usize,
) -> Vec<f64>

Generate dense time grid for AUC calculations

Creates a grid with:

• Observation times from the target
• Intermediate points at idelta intervals
• All times sorted and deduplicated

Arguments

• start_time - Start of time range
• end_time - End of time range
• obs_times - Required observation times (always included)
• idelta - Time step for dense grid (minutes)

Returns

Sorted, unique time vector suitable for AUC calculation