fix: resolve typecheck errors in loop_test.go and dingtalk_test.go (#2122)

- loop_test.go: replace undefined WithSecurity/SecurityConfig/ModelSecurityEntry
  with direct APIKeys field using SimpleSecureStrings()
- dingtalk_test.go: use ClientSecret.String() and ClientSecret.Set()
  instead of non-existent ClientSecret() and SetClientSecret() methods

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

pkg/agent/loop_test.go

@@ -1783,20 +1783,16 @@ func TestProcessMessage_ModelRoutingUsesLightProvider(t *testing.T) {
 				ModelName: "gemini-main",
 				Model:     "gemini/gemini-2.5-flash",
 				APIBase:   heavyServer.URL,
+				APIKeys:   config.SimpleSecureStrings("heavy-key"),
 			},
 			{
 				ModelName: "qwen-light",
 				Model:     "ollama/qwen2.5:0.5b",
 				APIBase:   lightServer.URL,
+				APIKeys:   config.SimpleSecureStrings("light-key"),
 			},
 		},
 	}
-	cfg.WithSecurity(&config.SecurityConfig{
-		ModelList: map[string]config.ModelSecurityEntry{
-			"gemini-main": {APIKeys: []string{"heavy-key"}},
-			"qwen-light":  {APIKeys: []string{"light-key"}},
-		},
-	})
 
 	msgBus := bus.NewMessageBus()
 	provider, _, err := providers.CreateProvider(cfg)

pkg/channels/dingtalk/dingtalk_test.go

@@ -17,8 +17,8 @@ func newTestDingTalkChannel(t *testing.T, cfg config.DingTalkConfig) (*DingTalkC
 	if cfg.ClientID == "" {
 		cfg.ClientID = "test-client-id"
 	}
-	if cfg.ClientSecret() == "" {
-		cfg.SetClientSecret("test-client-secret")
+	if cfg.ClientSecret.String() == "" {
+		cfg.ClientSecret.Set("test-client-secret")
 	}
 
 	msgBus := bus.NewMessageBus()