feat: refine operations UI and transport limits

gateway/internal/inbound/transport.go

@@ -12,6 +12,8 @@ import (
 	"time"
 )
 
+const maxAPIResponseBodyBytes int64 = 4 * 1024 * 1024
+
 func (s Server) post(ctx context.Context, path string, payload any, result any) error {
 	client := s.HTTPClient
 	if client == nil {
@@ -31,10 +33,17 @@ func (s Server) post(ctx context.Context, path string, payload any, result any)
 		return err
 	}
 	defer resp.Body.Close()
-	responseBody, err := io.ReadAll(io.LimitReader(resp.Body, 64*1024))
+	// Read one byte beyond the supported boundary so an oversized upstream
+	// response is reported explicitly. Silently cutting JSON at the boundary
+	// turns a transport-capacity problem into a misleading syntax error and can
+	// leave recoverable downstream receipts stuck indefinitely.
+	responseBody, err := io.ReadAll(io.LimitReader(resp.Body, maxAPIResponseBodyBytes+1))
 	if err != nil {
 		return fmt.Errorf("read api response: %w", err)
 	}
+	if int64(len(responseBody)) > maxAPIResponseBodyBytes {
+		return fmt.Errorf("api response exceeds %d-byte limit", maxAPIResponseBodyBytes)
+	}
 	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
 		detail := strings.TrimSpace(string(responseBody))
 		if detail == "" {