fix task duration recording

apps/api/internal/clients/clients_test.go

@@ -110,6 +110,7 @@ func TestOpenAIClientChatContract(t *testing.T) {
 			t.Fatalf("decode request: %v", err)
 		}
 		gotModel, _ = body["model"].(string)
+		time.Sleep(25 * time.Millisecond)
 		_ = json.NewEncoder(w).Encode(map[string]any{
 			"id":     "chatcmpl-test",
 			"object": "chat.completion",
@@ -145,6 +146,9 @@ func TestOpenAIClientChatContract(t *testing.T) {
 	if response.RequestID != "req-chat-test" || response.ResponseStartedAt.IsZero() || response.ResponseFinishedAt.IsZero() {
 		t.Fatalf("response metadata was not captured: %+v", response)
 	}
+	if response.ResponseDurationMS < 20 {
+		t.Fatalf("response duration should include upstream latency, got %dms", response.ResponseDurationMS)
+	}
 }
 
 func TestOpenAIClientChatStreamContract(t *testing.T) {