feat: add Agnes AI as default provider, support multi-provider switching

- Default provider changed from Zhipu to Agnes AI (agnes-2.0-flash)
- Add --provider flag: agnes (default), zhipu, custom
- Add AGNES_API_KEY env var support (still compatible with ZHIPU_API_KEY)
- Add provider presets system for easy switching between AI backends
- Add .gitignore to prevent config.json with API keys from being committed
- Update usage examples

Co-Authored-By: Claude <noreply@anthropic.com>

config.go

@@ -10,16 +10,48 @@ import (
 
 // Config holds the application configuration.
 type Config struct {
-	APIKey  string `json:"api_key"`
-	Model   string `json:"model"`
-	BaseURL string `json:"base_url"`
+	APIKey   string `json:"api_key"`
+	Model    string `json:"model"`
+	BaseURL  string `json:"base_url"`
+	Provider string `json:"provider"` // "agnes" or "zhipu" or "custom"
 }
 
-// DefaultConfig returns a Config with sensible defaults.
-func DefaultConfig() *Config {
-	return &Config{
+// Provider presets
+var providerPresets = map[string]struct {
+	Model   string
+	BaseURL string
+}{
+	"agnes": {
+		Model:   "agnes-2.0-flash",
+		BaseURL: "https://apihub.agnes-ai.com/v1/chat/completions",
+	},
+	"zhipu": {
 		Model:   "glm-4.6v-flash",
 		BaseURL: "https://open.bigmodel.cn/api/paas/v4/chat/completions",
+	},
+}
+
+// DefaultConfig returns a Config with sensible defaults (Agnes AI).
+func DefaultConfig() *Config {
+	return &Config{
+		Provider: "agnes",
+		Model:    "agnes-2.0-flash",
+		BaseURL:  "https://apihub.agnes-ai.com/v1/chat/completions",
+	}
+}
+
+// ApplyProvider applies a named provider preset, respecting user overrides.
+func (c *Config) ApplyProvider(provider string) {
+	if preset, ok := providerPresets[provider]; ok {
+		c.Provider = provider
+		// Only override model/baseURL if user hasn't set custom ones
+		if c.Model == "" || c.Model == "agnes-2.0-flash" || c.Model == "glm-4.6v-flash" {
+			c.Model = preset.Model
+		}
+		if c.BaseURL == "" || c.BaseURL == "https://apihub.agnes-ai.com/v1/chat/completions" ||
+			c.BaseURL == "https://open.bigmodel.cn/api/paas/v4/chat/completions" {
+			c.BaseURL = preset.BaseURL
+		}
 	}
 }
 
@@ -53,6 +85,9 @@ func LoadConfig(flagKey, configPath string) (*Config, error) {
 	}
 
 	// Override with environment variable
+	if envKey := os.Getenv("AGNES_API_KEY"); envKey != "" {
+		cfg.APIKey = envKey
+	}
 	if envKey := os.Getenv("ZHIPU_API_KEY"); envKey != "" {
 		cfg.APIKey = envKey
 	}
@@ -65,7 +100,7 @@ func LoadConfig(flagKey, configPath string) (*Config, error) {
 	if cfg.APIKey == "" {
 		return cfg, fmt.Errorf("API key not configured. Set it via:\n" +
 			"  1. --apikey flag\n" +
-			"  2. ZHIPU_API_KEY environment variable\n" +
+			"  2. AGNES_API_KEY environment variable\n" +
 			"  3. config.json file in the tools directory")
 	}