some fixes

reporter/reporter.go

@@ -86,6 +86,13 @@ func writeBuildText(w io.Writer, b *runner.BuildRun, multi bool) {
 					fmt.Fprintf(w, "│      %s\n", line)
 				}
 			}
+
+			if tr.Status != runner.StatusPass && strings.TrimSpace(tr.ActualStderr) != "" {
+				fmt.Fprintf(w, "│      ── stderr ──\n")
+				for _, line := range clampLines(tr.ActualStderr, 10) {
+					fmt.Fprintf(w, "│      %s\n", line)
+				}
+			}
 		}
 		fmt.Fprintf(w, "└─\n")
 	}
@@ -265,6 +272,18 @@ func extractTotalScore(data []byte) (float64, error) {
 	return header.TotalScore, nil
 }
 
+// clampLines returns up to max lines of s (trailing newline ignored), appending
+// a truncation note when more lines were omitted.
+func clampLines(s string, max int) []string {
+	s = strings.TrimRight(s, "\n")
+	lines := strings.Split(s, "\n")
+	if len(lines) <= max {
+		return lines
+	}
+	out := append([]string{}, lines[:max]...)
+	return append(out, fmt.Sprintf("... (%d more lines)", len(lines)-max))
+}
+
 func humanBytes(n int64) string {
 	const (
 		KiB = 1024