calibrate

type CalibrationReport struct {
	OverallFactor float64              // recommended global calibration factor
	ByRole        []RoleStat           // per-role breakdown (first entry is "all")
	Suggestions   []EstimateSuggestion // AI suggestions for pending tasks
}

type EstimateSuggestion struct {
	TaskID     int    `json:"task_id"`
	Title      string `json:"title"`
	OldMinutes int    `json:"old_minutes"`
	NewMinutes int    `json:"new_minutes"`
	Reasoning  string `json:"reasoning"`
}

type RoleStat struct {
	Role        string
	TaskCount   int
	EstTotal    int     // sum of EstimatedMinutes
	ActualTotal int     // sum of ActualMinutes
	MAE         float64 // mean absolute error in minutes
	Bias        float64 // mean(actual - estimated); positive = underestimated
	Factor      float64 // ActualTotal / EstTotal; 1.0 = perfect, >1 = underestimate
}