An artifact may name which stage of its recipe to stop at

One source, two images, deliberately different: a toolchain carries a compiler
and the image the same module runs in should not.

internal/catalogue/manifest.go

@@ -380,6 +380,15 @@ type Artifact struct {
 	// From is what it is built from, relative to the repository root: a Dockerfile for an image,
 	// a directory for an archive.
 	From string `json:"from"`
+	// Target is which stage of that Dockerfile to stop at, for a recipe that describes more than
+	// one image.
+	//
+	// **One source, two images, and they are meant to differ.** A toolchain image carries a
+	// compiler and everything a build needs; the image the same module *runs* in should carry
+	// neither. Describing both in one recipe keeps them in step — they share a base, a library
+	// version and an operating system — while letting each be built and published separately.
+	// Empty means the whole recipe, which is what a module with one image says by saying nothing.
+	Target string `json:"target,omitempty"`
 }
 
 // Kinds an artifact may be.