Add run manifest and logical output file contracts

internal/framework/contracts/composition_test.go

@@ -124,10 +124,13 @@ func TestContractsComposeAcrossPackages(t *testing.T) {
 	if err != nil {
 		t.Fatalf("Encode() error = %v, want nil", err)
 	}
-	if output.ContentType != "application/json" {
-		t.Fatalf("ContentType = %q, want application/json", output.ContentType)
+	if len(output.Files) != 1 {
+		t.Fatalf("len(Files) = %d, want 1", len(output.Files))
 	}
-	if len(output.Bytes) == 0 {
+	if output.Files[0].ContentType != "application/json" {
+		t.Fatalf("ContentType = %q, want application/json", output.Files[0].ContentType)
+	}
+	if len(output.Files[0].Bytes) == 0 {
 		t.Fatal("len(Bytes) = 0, want encoded bytes")
 	}
 }
@@ -293,7 +296,12 @@ func (encoder compositionOutputEncoder) Encode(ctx context.Context, req contract
 	}
 
 	return contracts.OutputResult{
-		Bytes:       encoded,
-		ContentType: "application/json",
+		Files: []contracts.OutputFile{
+			{
+				Name:        "artifacts/generic.json",
+				ContentType: "application/json",
+				Bytes:       encoded,
+			},
+		},
 	}, nil
 }