fix: accept non-marker stderr in kiro fallback

When stdout has no review marker, fall back to stderr
unconditionally (not only when stderr also has a marker).
This handles the case where stderr contains plain review
text without Kiro chrome.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: wesm

internal/agent/kiro.go

@@ -166,11 +166,11 @@ func (a *KiroAgent) Review(ctx context.Context, repoPath, commitSHA, prompt stri
 	}
 
 	// Prefer the stream that contains a "> " review marker.
-	// Stdout noise without a marker should not block the
-	// stderr fallback.
+	// When stdout has no marker (noise-only) or is empty,
+	// fall back to stderr unconditionally.
 	result, hasMarker := stripKiroReview(stdout.String())
 	if !hasMarker || len(result) == 0 {
-		if alt, ok := stripKiroReview(stderr.String()); ok && len(alt) > 0 {
+		if alt, _ := stripKiroReview(stderr.String()); len(alt) > 0 {
 			result = alt
 		}
 	}

internal/agent/kiro_test.go

@@ -411,6 +411,34 @@ func TestKiroReviewStderrPreferredOverStdoutNoise(t *testing.T) {
 	}
 }
 
+func TestKiroReviewStderrFallbackNoMarker(t *testing.T) {
+	skipIfWindows(t)
+
+	// stdout has noise without a marker; stderr has plain
+	// review text also without a marker. stderr should still
+	// be preferred over stdout noise.
+	script := NewScriptBuilder().
+		AddRaw(`echo "Loading model..."`).
+		AddRaw(`echo "review text without marker" >&2`).
+		Build()
+	cmdPath := writeTempCommand(t, script)
+	a := NewKiroAgent(cmdPath)
+
+	result, err := a.Review(
+		context.Background(), t.TempDir(),
+		"deadbeef", "review", nil,
+	)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if !strings.Contains(result, "review text without marker") {
+		t.Fatalf(
+			"expected stderr fallback even without marker, got: %q",
+			result,
+		)
+	}
+}
+
 func TestKiroReviewPromptTooLarge(t *testing.T) {
 	a := NewKiroAgent("kiro-cli")
 	bigPrompt := strings.Repeat("x", maxPromptArgLen+1)