dag

type Analysis struct {
	Steps          []StepInfo
	ExecutionOrder [][]string // layers of parallelizable steps
	MaxParallelism int
	RootSteps      []string // steps with no predecessors
	LeafSteps      []string // steps with no successors
}

type StepInfo struct {
	Name       string
	Engine     string
	Image      string
	DependsOn  []string
	Successors []string
	Depth      int // topological depth (layer index)
}