fix: improve seedance reference handling

handler/ai_test.go

@@ -0,0 +1,20 @@
+package handler
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestAIUpstreamErrorDetail(t *testing.T) {
+	got := aiUpstreamErrorDetail([]byte(`{"error":{"code":"InvalidParameter","message":"reference video fps is invalid"}}`))
+	if got != "InvalidParameter reference video fps is invalid" {
+		t.Fatalf("detail = %q", got)
+	}
+}
+
+func TestSafeUpstreamTextTruncates(t *testing.T) {
+	got := safeUpstreamText(strings.Repeat("错", 320))
+	if len([]rune(got)) != 303 {
+		t.Fatalf("truncated rune length = %d", len([]rune(got)))
+	}
+}