refactor(mcp) (#1042)

* improve(interface): replace with interface

* feat(mcp): 添加构建器模式支持

新增功能：
- RequestBuilder 构建器，支持流式 API
- 多轮对话支持（AddAssistantMessage）
- Function Calling / Tools 支持
- 精细参数控制（temperature, top_p, penalties 等）
- 3个预设场景（Chat, CodeGen, CreativeWriting）
- 完整的测试套件（19个新测试）

修复问题：
- Config 字段未使用（MaxRetries、Temperature 等）
- DeepSeek/Qwen SetAPIKey 的冗余 nil 检查

向后兼容：
- 保留 CallWithMessages API
- 新增 CallWithRequest API

测试：
- 81 个测试全部通过
- 覆盖率 80.6%

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: tinkle-community <tinklefund@gmail.com>

---------

Co-authored-by: zbhan <zbhan@freewheel.tv>
Co-authored-by: tinkle-community <tinklefund@gmail.com>

mcp/options.go

@@ -0,0 +1,162 @@
+package mcp
+
+import (
+	"net/http"
+	"time"
+)
+
+// ClientOption 客户端选项函数（Functional Options 模式）
+type ClientOption func(*Config)
+
+// ============================================================
+// 依赖注入选项
+// ============================================================
+
+// WithLogger 设置自定义日志器
+//
+// 使用示例：
+//   client := mcp.NewClient(mcp.WithLogger(customLogger))
+func WithLogger(logger Logger) ClientOption {
+	return func(c *Config) {
+		c.Logger = logger
+	}
+}
+
+// WithHTTPClient 设置自定义 HTTP 客户端
+//
+// 使用示例：
+//   httpClient := &http.Client{Timeout: 60 * time.Second}
+//   client := mcp.NewClient(mcp.WithHTTPClient(httpClient))
+func WithHTTPClient(client *http.Client) ClientOption {
+	return func(c *Config) {
+		c.HTTPClient = client
+	}
+}
+
+// ============================================================
+// 超时和重试选项
+// ============================================================
+
+// WithTimeout 设置请求超时时间
+//
+// 使用示例：
+//   client := mcp.NewClient(mcp.WithTimeout(60 * time.Second))
+func WithTimeout(timeout time.Duration) ClientOption {
+	return func(c *Config) {
+		c.Timeout = timeout
+		c.HTTPClient.Timeout = timeout
+	}
+}
+
+// WithMaxRetries 设置最大重试次数
+//
+// 使用示例：
+//   client := mcp.NewClient(mcp.WithMaxRetries(5))
+func WithMaxRetries(maxRetries int) ClientOption {
+	return func(c *Config) {
+		c.MaxRetries = maxRetries
+	}
+}
+
+// WithRetryWaitBase 设置重试等待基础时长
+//
+// 使用示例：
+//   client := mcp.NewClient(mcp.WithRetryWaitBase(3 * time.Second))
+func WithRetryWaitBase(waitTime time.Duration) ClientOption {
+	return func(c *Config) {
+		c.RetryWaitBase = waitTime
+	}
+}
+
+// ============================================================
+// AI 参数选项
+// ============================================================
+
+// WithMaxTokens 设置最大 token 数
+//
+// 使用示例：
+//   client := mcp.NewClient(mcp.WithMaxTokens(4000))
+func WithMaxTokens(maxTokens int) ClientOption {
+	return func(c *Config) {
+		c.MaxTokens = maxTokens
+	}
+}
+
+// WithTemperature 设置温度参数
+//
+// 使用示例：
+//   client := mcp.NewClient(mcp.WithTemperature(0.7))
+func WithTemperature(temperature float64) ClientOption {
+	return func(c *Config) {
+		c.Temperature = temperature
+	}
+}
+
+// ============================================================
+// Provider 配置选项
+// ============================================================
+
+// WithAPIKey 设置 API Key
+func WithAPIKey(apiKey string) ClientOption {
+	return func(c *Config) {
+		c.APIKey = apiKey
+	}
+}
+
+// WithBaseURL 设置基础 URL
+func WithBaseURL(baseURL string) ClientOption {
+	return func(c *Config) {
+		c.BaseURL = baseURL
+	}
+}
+
+// WithModel 设置模型名称
+func WithModel(model string) ClientOption {
+	return func(c *Config) {
+		c.Model = model
+	}
+}
+
+// WithProvider 设置提供商
+func WithProvider(provider string) ClientOption {
+	return func(c *Config) {
+		c.Provider = provider
+	}
+}
+
+// WithUseFullURL 设置是否使用完整 URL
+func WithUseFullURL(useFullURL bool) ClientOption {
+	return func(c *Config) {
+		c.UseFullURL = useFullURL
+	}
+}
+
+// ============================================================
+// 组合选项（便捷方法）
+// ============================================================
+
+// WithDeepSeekConfig 设置 DeepSeek 配置
+//
+// 使用示例：
+//   client := mcp.NewClient(mcp.WithDeepSeekConfig("sk-xxx"))
+func WithDeepSeekConfig(apiKey string) ClientOption {
+	return func(c *Config) {
+		c.Provider = ProviderDeepSeek
+		c.APIKey = apiKey
+		c.BaseURL = DefaultDeepSeekBaseURL
+		c.Model = DefaultDeepSeekModel
+	}
+}
+
+// WithQwenConfig 设置 Qwen 配置
+//
+// 使用示例：
+//   client := mcp.NewClient(mcp.WithQwenConfig("sk-xxx"))
+func WithQwenConfig(apiKey string) ClientOption {
+	return func(c *Config) {
+		c.Provider = ProviderQwen
+		c.APIKey = apiKey
+		c.BaseURL = DefaultQwenBaseURL
+		c.Model = DefaultQwenModel
+	}
+}