feat: release v0.26 portable i18n and presentation adapters

response/config.go

@@ -187,6 +187,9 @@ func (f *Formatter) Value(r Result) map[string]any {
 	if isError && r.BusinessCode != nil {
 		code, message = r.BusinessCode, r.Message
 	}
+	if r.MessageOverride != nil {
+		message = *r.MessageOverride
+	}
 	body := c.Body
 	if isError && c.ErrorBody != nil {
 		body = c.ErrorBody

response/encoder.go

@@ -16,6 +16,10 @@ type Result struct {
 	Err                      error
 	BusinessCode             any
 	Failed                   bool
+	// MessageOverride is optional localized presentation. Message remains the
+	// canonical catalog text for validation. Custom protocols opt in by calling
+	// PublicMessage; fixed acknowledgments remain under their encoder's control.
+	MessageOverride *string
 	// PreserveStatus keeps an explicit protocol status through catalog mapping
 	// and HTTP output (for example, readiness must remain 503 when unhealthy).
 	PreserveStatus bool
@@ -24,6 +28,13 @@ type Result struct {
 // IsError preserves failure semantics independently of the HTTP status.
 func (r Result) IsError() bool { return r.Failed || r.Err != nil || r.Status >= 400 }
 
+func (r Result) PublicMessage() string {
+	if r.MessageOverride != nil {
+		return *r.MessageOverride
+	}
+	return r.Message
+}
+
 // Payload is a complete response. Encoders must be safe for concurrent use.
 // Status and headers are intentionally part of the contract: callback protocols
 // may acknowledge an error using a different HTTP status or media type.