Version: 0.9.65.dev.260503

后端：
1. 阶段 1.5/1.6
收口 llm-service / rag-service，统一模型出口与检索基础设施入口，清退 backend/infra/llm 与 backend/infra/rag 旧实现；
2. 同步更新相关调用链与微服务迁移计划文档

backend/services/llm/ark_adapter.go

@@ -0,0 +1,111 @@
+package llm
+
+import (
+	"context"
+	"errors"
+	"io"
+
+	"github.com/cloudwego/eino-ext/components/model/ark"
+	einoModel "github.com/cloudwego/eino/components/model"
+	"github.com/cloudwego/eino/schema"
+	arkModel "github.com/volcengine/volcengine-go-sdk/service/arkruntime/model"
+)
+
+// WrapArkClient 将 ark.ChatModel 适配为统一 Client。
+// 1. generateText 走 Generate，供 GenerateJSON/GenerateText 使用。
+// 2. streamText 走 Stream，供需要流式输出的场景使用。
+// 3. 两条路径共用同一套参数转换逻辑。
+func WrapArkClient(arkChatModel *ark.ChatModel) *Client {
+	if arkChatModel == nil {
+		return nil
+	}
+
+	generateFunc := func(ctx context.Context, messages []*schema.Message, options GenerateOptions) (*TextResult, error) {
+		arkOpts := buildArkStreamOptions(options)
+		msg, err := arkChatModel.Generate(ctx, messages, arkOpts...)
+		if err != nil {
+			return nil, err
+		}
+		if msg == nil {
+			return nil, errors.New("ark model returned nil message")
+		}
+
+		var usage *schema.TokenUsage
+		finishReason := ""
+		if msg.ResponseMeta != nil {
+			usage = CloneUsage(msg.ResponseMeta.Usage)
+			finishReason = msg.ResponseMeta.FinishReason
+		}
+
+		return &TextResult{
+			Text:         msg.Content,
+			Usage:        usage,
+			FinishReason: finishReason,
+		}, nil
+	}
+
+	streamFunc := func(ctx context.Context, messages []*schema.Message, options GenerateOptions) (StreamReader, error) {
+		arkOpts := buildArkStreamOptions(options)
+		reader, err := arkChatModel.Stream(ctx, messages, arkOpts...)
+		if err != nil {
+			return nil, err
+		}
+		return &arkStreamReaderAdapter{reader: reader}, nil
+	}
+
+	return NewClient(generateFunc, streamFunc)
+}
+
+// buildArkStreamOptions 将统一的 GenerateOptions 转换为 ark 的流式调用参数。
+func buildArkStreamOptions(options GenerateOptions) []einoModel.Option {
+	thinkingEnabled := options.Thinking == ThinkingModeEnabled
+
+	thinkingType := arkModel.ThinkingTypeDisabled
+	if thinkingEnabled {
+		thinkingType = arkModel.ThinkingTypeEnabled
+	}
+	opts := []einoModel.Option{
+		ark.WithThinking(&arkModel.Thinking{Type: thinkingType}),
+	}
+
+	if thinkingEnabled {
+		opts = append(opts, einoModel.WithTemperature(1.0))
+	} else if options.Temperature > 0 {
+		opts = append(opts, einoModel.WithTemperature(float32(options.Temperature)))
+	}
+
+	maxTokens := options.MaxTokens
+	if thinkingEnabled {
+		const minThinkingBudget = 16000
+		if maxTokens < minThinkingBudget {
+			maxTokens = minThinkingBudget
+		}
+	}
+	if maxTokens > 0 {
+		opts = append(opts, einoModel.WithMaxTokens(maxTokens))
+	}
+
+	return opts
+}
+
+// arkStreamReaderAdapter 把 ark 的流式 reader 转成统一的 StreamReader 接口。
+type arkStreamReaderAdapter struct {
+	reader *schema.StreamReader[*schema.Message]
+}
+
+// Recv 转发到底层 reader。
+func (r *arkStreamReaderAdapter) Recv() (*schema.Message, error) {
+	if r == nil || r.reader == nil {
+		return nil, io.EOF
+	}
+	return r.reader.Recv()
+}
+
+// Close 适配 ark reader 的 Close 行为。
+func (r *arkStreamReaderAdapter) Close() error {
+	if r == nil || r.reader == nil {
+		return nil
+	}
+	r.reader.Close()
+	return nil
+}