feat: add CompareVariants for responsive imprint analysis

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

pipeline.go

@@ -45,3 +45,31 @@ func Imprint(node Node, ctx *Context) reversal.GrammarImprint {
 	tokens := tok.Tokenise(text)
 	return reversal.NewImprint(tokens)
 }
+
+// CompareVariants runs the imprint pipeline on each responsive variant independently
+// and returns pairwise similarity scores. Key format: "name1:name2".
+func CompareVariants(r *Responsive, ctx *Context) map[string]float64 {
+	if ctx == nil {
+		ctx = NewContext()
+	}
+
+	type named struct {
+		name string
+		imp  reversal.GrammarImprint
+	}
+
+	var imprints []named
+	for _, v := range r.variants {
+		imp := Imprint(v.layout, ctx)
+		imprints = append(imprints, named{name: v.name, imp: imp})
+	}
+
+	scores := make(map[string]float64)
+	for i := 0; i < len(imprints); i++ {
+		for j := i + 1; j < len(imprints); j++ {
+			key := imprints[i].name + ":" + imprints[j].name
+			scores[key] = imprints[i].imp.Similar(imprints[j].imp)
+		}
+	}
+	return scores
+}

pipeline_test.go

@@ -99,3 +99,30 @@ func TestImprint_SimilarPages(t *testing.T) {
 		t.Errorf("similar pages should score higher (%f) than different (%f)", sim, diffSim)
 	}
 }
+
+func TestCompareVariants(t *testing.T) {
+	svc, _ := i18n.New()
+	i18n.SetDefault(svc)
+	ctx := NewContext()
+
+	r := NewResponsive().
+		Variant("desktop", NewLayout("HLCRF").
+			H(El("h1", Text("Building project"))).
+			C(El("p", Text("Files deleted successfully"))).
+			F(El("small", Text("Completed")))).
+		Variant("mobile", NewLayout("HCF").
+			H(El("h1", Text("Building project"))).
+			C(El("p", Text("Files deleted successfully"))).
+			F(El("small", Text("Completed"))))
+
+	scores := CompareVariants(r, ctx)
+
+	key := "desktop:mobile"
+	sim, ok := scores[key]
+	if !ok {
+		t.Fatalf("CompareVariants missing key %q, got keys: %v", key, scores)
+	}
+	if sim < 0.8 {
+		t.Errorf("same content in different variants should score >= 0.8, got %f", sim)
+	}
+}