feat: Go 图片识别 CLI 工具 — 对接 Agnes-2.0-Flash 免费视觉模型

为 Claude Code 等 AI 编码助手提供图片理解能力：
- 支持本地图片 base64 编码上传
- 多图对比分析
- 自动重试 + 指数退避
- 多源配置管理（命令行/环境变量/配置文件）
- 关闭 thinking 模式以降低延迟

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

config.go

@@ -0,0 +1,106 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+// Config holds the application configuration.
+type Config struct {
+	APIKey  string `json:"api_key"`
+	Model   string `json:"model"`
+	BaseURL string `json:"base_url"`
+}
+
+// DefaultConfig returns a Config with sensible defaults.
+func DefaultConfig() *Config {
+	return &Config{
+		Model:   "glm-4.6v-flash",
+		BaseURL: "https://open.bigmodel.cn/api/paas/v4/chat/completions",
+	}
+}
+
+// LoadConfig loads configuration from multiple sources in priority order:
+// 1. Command-line --apikey flag (highest)
+// 2. ZHIPU_API_KEY environment variable
+// 3. config.json in the same directory as the executable
+// 4. Default built-in key (lowest)
+func LoadConfig(flagKey, configPath string) (*Config, error) {
+	cfg := DefaultConfig()
+
+	// Load from config file if it exists (lowest priority)
+	if configPath == "" {
+		execDir := getExecDir()
+		configPath = filepath.Join(execDir, "config.json")
+	}
+
+	if data, err := os.ReadFile(configPath); err == nil {
+		var fileCfg Config
+		if err := json.Unmarshal(data, &fileCfg); err == nil {
+			if fileCfg.APIKey != "" {
+				cfg.APIKey = fileCfg.APIKey
+			}
+			if fileCfg.Model != "" {
+				cfg.Model = fileCfg.Model
+			}
+			if fileCfg.BaseURL != "" {
+				cfg.BaseURL = fileCfg.BaseURL
+			}
+		}
+	}
+
+	// Override with environment variable
+	if envKey := os.Getenv("ZHIPU_API_KEY"); envKey != "" {
+		cfg.APIKey = envKey
+	}
+
+	// Highest priority: command-line flag
+	if flagKey != "" {
+		cfg.APIKey = flagKey
+	}
+
+	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" +
+			"  3. config.json file in the tools directory")
+	}
+
+	return cfg, nil
+}
+
+// SaveConfigFile saves config to a JSON file.
+func SaveConfigFile(path, apiKey string) error {
+	cfg := DefaultConfig()
+	cfg.APIKey = apiKey
+
+	data, err := json.MarshalIndent(cfg, "", "  ")
+	if err != nil {
+		return err
+	}
+
+	if err := os.MkdirAll(filepath.Dir(path), 0755); err != nil {
+		return err
+	}
+
+	return os.WriteFile(path, data, 0600)
+}
+
+func getExecDir() string {
+	execPath, err := os.Executable()
+	if err != nil {
+		return "."
+	}
+	return filepath.Dir(execPath)
+}
+
+// MaskKey masks the API key for safe display, showing only first 8 and last 4 chars.
+func MaskKey(key string) string {
+	if len(key) <= 12 {
+		return strings.Repeat("*", len(key))
+	}
+	return key[:8] + "..." + key[len(key)-4:]
+}