vm

type Cell struct {
	// Key is the document identity (filesystem-style relative path).
	Key string

	// Value is the polymorphic content (Text, Json, List, Binary).
	Value Gist

	// Steps holds named outputs from prior steps (shared across cells).
	// Downstream stages reference these via Go templates (e.g., {{.steps.extract}}).
	Steps map[string]Gist

	// Env holds environment/metadata key-value pairs.
	Env map[string]any
}

type Gist interface {
	ContentType() string
}