refactor(materials): optimize UTF-8 check and add binary round-trip test

Check UTF-8 validity before allocating string to avoid wasted allocation
for binary content. Add round-trip test verifying binary data survives
the structpb.Struct serialization path.

Signed-off-by: Miguel Martinez Trivino <miguel@chainloop.dev>

Author: migmartri

app/cli/pkg/action/workflow_run_describe.go

@@ -318,18 +318,16 @@ func materialPBToAction(in *pb.AttestationItem_Material) *Material {
 	// Fall back to deprecated string value field for compatibility with
 	// older control plane versions that don't populate raw_value.
 	var value string
-	if len(in.GetRawValue()) > 0 {
-		value = string(in.GetRawValue())
-		if !utf8.Valid(in.GetRawValue()) {
-			value = ""
+	if raw := in.GetRawValue(); len(raw) > 0 {
+		if utf8.Valid(raw) {
+			value = string(raw)
 		}
 	} else {
 		value = in.GetValue() //nolint:staticcheck // fallback for older servers
 	}
 
 	m := &Material{
-		Name: in.Name,
-		// kept for compatibility in case we have users that are still using the string value field
+		Name:           in.Name,
 		Value:          value,
 		RawValue:       in.GetRawValue(),
 		Type:           in.Type,

pkg/attestation/renderer/chainloop/v02_test.go

@@ -351,7 +351,7 @@ func TestBinaryContentStructRoundTrip(t *testing.T) {
 				Materials: []*intoto.ResourceDescriptor{
 					{
 						Name: "binary.bin",
-						Annotations: mapToStruct(t, map[string]interface{}{
+						Annotations: mapToStruct(t, map[string]any{
 							"chainloop.material.name":       "test-binary",
 							"chainloop.material.type":       "ARTIFACT",
 							"chainloop.material.cas.inline": true,