fix(providers): address LongCat review feedback

- Add dedicated factory routing test for LongCat provider
- Add longcat to DefaultAPIBase test coverage
- Set default api_base in example config providers section

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

config/config.example.json

@@ -282,7 +282,7 @@
     },
     "longcat": {
       "api_key": "",
-      "api_base": ""
+      "api_base": "https://api.longcat.chat/openai"
     }
   },
   "tools": {

pkg/providers/factory_provider_test.go

@@ -113,6 +113,7 @@ func TestCreateProviderFromConfig_DefaultAPIBase(t *testing.T) {
 		{"vllm", "vllm"},
 		{"deepseek", "deepseek"},
 		{"ollama", "ollama"},
+		{"longcat", "longcat"},
 	}
 
 	for _, tt := range tests {
@@ -162,6 +163,29 @@ func TestCreateProviderFromConfig_LiteLLM(t *testing.T) {
 	}
 }
 
+func TestCreateProviderFromConfig_LongCat(t *testing.T) {
+	cfg := &config.ModelConfig{
+		ModelName: "test-longcat",
+		Model:     "longcat/LongCat-Flash-Thinking",
+		APIKey:    "test-key",
+		APIBase:   "https://api.longcat.chat/openai",
+	}
+
+	provider, modelID, err := CreateProviderFromConfig(cfg)
+	if err != nil {
+		t.Fatalf("CreateProviderFromConfig() error = %v", err)
+	}
+	if provider == nil {
+		t.Fatal("CreateProviderFromConfig() returned nil provider")
+	}
+	if modelID != "LongCat-Flash-Thinking" {
+		t.Errorf("modelID = %q, want %q", modelID, "LongCat-Flash-Thinking")
+	}
+	if _, ok := provider.(*HTTPProvider); !ok {
+		t.Fatalf("expected *HTTPProvider, got %T", provider)
+	}
+}
+
 func TestCreateProviderFromConfig_Anthropic(t *testing.T) {
 	cfg := &config.ModelConfig{
 		ModelName: "test-anthropic",