feat: record task attempt chains

apps/api/internal/httpapi/core_flow_integration_test.go

@@ -722,6 +722,31 @@ WHERE reference_type = 'gateway_task'
 	if failoverTask.Task.Status != "succeeded" {
 		t.Fatalf("failover task should succeed through second client: %+v", failoverTask.Task)
 	}
+	var failoverDetail struct {
+		Attempts []struct {
+			AttemptNo    int    `json:"attemptNo"`
+			PlatformName string `json:"platformName"`
+			Status       string `json:"status"`
+			Retryable    bool   `json:"retryable"`
+			ErrorCode    string `json:"errorCode"`
+			ErrorMessage string `json:"errorMessage"`
+			ResponseMS   int64  `json:"responseDurationMs"`
+		} `json:"attempts"`
+		Metrics map[string]any `json:"metrics"`
+	}
+	doJSON(t, server.URL, http.MethodGet, "/api/v1/tasks/"+failoverTask.Task.ID, apiKeyResponse.Secret, nil, http.StatusOK, &failoverDetail)
+	if len(failoverDetail.Attempts) != 2 {
+		t.Fatalf("failover task history should include two attempts, got %+v", failoverDetail.Attempts)
+	}
+	if failoverDetail.Attempts[0].PlatformName != "OpenAI Retryable Failure" || failoverDetail.Attempts[0].Status != "failed" || !failoverDetail.Attempts[0].Retryable || failoverDetail.Attempts[0].ErrorCode == "" {
+		t.Fatalf("first failover attempt should preserve failed platform and reason: %+v", failoverDetail.Attempts[0])
+	}
+	if failoverDetail.Attempts[1].PlatformName != "OpenAI Retry Success" || failoverDetail.Attempts[1].Status != "succeeded" || failoverDetail.Attempts[1].ResponseMS <= 0 {
+		t.Fatalf("second failover attempt should preserve successful platform: %+v", failoverDetail.Attempts[1])
+	}
+	if summary, ok := failoverDetail.Metrics["attempts"].([]any); !ok || len(summary) != 2 {
+		t.Fatalf("task metrics should keep attempt-chain summary, got %+v", failoverDetail.Metrics)
+	}
 
 	var degradePolicySet struct {
 		ID string `json:"id"`