feat: 配置 golangci-lint 静态分析并修复存量违规

- 新增 backend/.golangci.yml 配置 12 个 linter（forbidigo、errorlint、errcheck、staticcheck、revive、gocritic、gosec、bodyclose、noctx、nilerr、goimports、gocyclo）
- 新增 lefthook.yml 配置 pre-commit hook 自动运行 lint
- 修复存量代码违规：errors.Is/As 替换、zap.Error 替换、import 排序、errcheck 修复
- 更新 README 补充编码规范说明
- 归档 backend-code-lint 变更

backend/internal/conversion/anthropic/decoder.go

@@ -28,7 +28,10 @@ func decodeRequest(body []byte) (*canonical.CanonicalRequest, error) {
 
 	var canonicalMsgs []canonical.CanonicalMessage
 	for _, msg := range req.Messages {
-		decoded := decodeMessage(msg)
+		decoded, err := decodeMessage(msg)
+		if err != nil {
+			return nil, conversion.NewConversionError(conversion.ErrorCodeJSONParseError, "解析消息内容失败").WithCause(err)
+		}
 		canonicalMsgs = append(canonicalMsgs, decoded...)
 	}
 
@@ -94,10 +97,13 @@ func decodeSystem(system any) any {
 }
 
 // decodeMessage 解码 Anthropic 消息
-func decodeMessage(msg Message) []canonical.CanonicalMessage {
+func decodeMessage(msg Message) ([]canonical.CanonicalMessage, error) {
 	switch msg.Role {
 	case "user":
-		blocks := decodeContentBlocks(msg.Content)
+		blocks, err := decodeContentBlocks(msg.Content)
+		if err != nil {
+			return nil, err
+		}
 		var toolResults []canonical.ContentBlock
 		var others []canonical.ContentBlock
 		for _, b := range blocks {
@@ -117,58 +123,83 @@ func decodeMessage(msg Message) []canonical.CanonicalMessage {
 		if len(result) == 0 {
 			result = append(result, canonical.CanonicalMessage{Role: canonical.RoleUser, Content: []canonical.ContentBlock{canonical.NewTextBlock("")}})
 		}
-		return result
+		return result, nil
 
 	case "assistant":
-		blocks := decodeContentBlocks(msg.Content)
+		blocks, err := decodeContentBlocks(msg.Content)
+		if err != nil {
+			return nil, err
+		}
 		if len(blocks) == 0 {
 			blocks = append(blocks, canonical.NewTextBlock(""))
 		}
-		return []canonical.CanonicalMessage{{Role: canonical.RoleAssistant, Content: blocks}}
+		return []canonical.CanonicalMessage{{Role: canonical.RoleAssistant, Content: blocks}}, nil
 	}
-	return nil
+	return nil, nil
 }
 
 // decodeContentBlocks 解码内容块列表
-func decodeContentBlocks(content any) []canonical.ContentBlock {
+func decodeContentBlocks(content any) ([]canonical.ContentBlock, error) {
 	switch v := content.(type) {
 	case string:
-		return []canonical.ContentBlock{canonical.NewTextBlock(v)}
+		return []canonical.ContentBlock{canonical.NewTextBlock(v)}, nil
 	case []any:
 		var blocks []canonical.ContentBlock
 		for _, item := range v {
 			if m, ok := item.(map[string]any); ok {
-				block := decodeSingleContentBlock(m)
+				block, err := decodeSingleContentBlock(m)
+				if err != nil {
+					return nil, err
+				}
 				if block != nil {
 					blocks = append(blocks, *block)
 				}
 			}
 		}
 		if len(blocks) > 0 {
-			return blocks
+			return blocks, nil
 		}
-		return []canonical.ContentBlock{canonical.NewTextBlock("")}
+		return []canonical.ContentBlock{canonical.NewTextBlock("")}, nil
 	case nil:
-		return []canonical.ContentBlock{canonical.NewTextBlock("")}
+		return []canonical.ContentBlock{canonical.NewTextBlock("")}, nil
 	default:
-		return []canonical.ContentBlock{canonical.NewTextBlock(fmt.Sprintf("%v", v))}
+		return []canonical.ContentBlock{canonical.NewTextBlock(fmt.Sprintf("%v", v))}, nil
 	}
 }
 
 // decodeSingleContentBlock 解码单个内容块
-func decodeSingleContentBlock(m map[string]any) *canonical.ContentBlock {
-	t, _ := m["type"].(string)
+func decodeSingleContentBlock(m map[string]any) (*canonical.ContentBlock, error) {
+	t, ok := m["type"].(string)
+	if !ok {
+		return nil, nil
+	}
+
 	switch t {
 	case "text":
-		text, _ := m["text"].(string)
-		return &canonical.ContentBlock{Type: "text", Text: text}
+		text, ok := m["text"].(string)
+		if !ok {
+			text = ""
+		}
+		return &canonical.ContentBlock{Type: "text", Text: text}, nil
 	case "tool_use":
-		id, _ := m["id"].(string)
-		name, _ := m["name"].(string)
-		input, _ := json.Marshal(m["input"])
-		return &canonical.ContentBlock{Type: "tool_use", ID: id, Name: name, Input: input}
+		id, ok := m["id"].(string)
+		if !ok {
+			id = ""
+		}
+		name, ok := m["name"].(string)
+		if !ok {
+			name = ""
+		}
+		input, err := json.Marshal(m["input"])
+		if err != nil {
+			return nil, err
+		}
+		return &canonical.ContentBlock{Type: "tool_use", ID: id, Name: name, Input: input}, nil
 	case "tool_result":
-		toolUseID, _ := m["tool_use_id"].(string)
+		toolUseID, ok := m["tool_use_id"].(string)
+		if !ok {
+			toolUseID = ""
+		}
 		isErr := false
 		if ie, ok := m["is_error"].(bool); ok {
 			isErr = ie
@@ -179,7 +210,11 @@ func decodeSingleContentBlock(m map[string]any) *canonical.ContentBlock {
 			case string:
 				content = json.RawMessage(fmt.Sprintf("%q", cv))
 			default:
-				content, _ = json.Marshal(cv)
+				encoded, err := json.Marshal(cv)
+				if err != nil {
+					return nil, err
+				}
+				content = encoded
 			}
 		} else {
 			content = json.RawMessage(`""`)
@@ -189,15 +224,18 @@ func decodeSingleContentBlock(m map[string]any) *canonical.ContentBlock {
 			ToolUseID: toolUseID,
 			Content:   content,
 			IsError:   &isErr,
-		}
+		}, nil
 	case "thinking":
-		thinking, _ := m["thinking"].(string)
-		return &canonical.ContentBlock{Type: "thinking", Thinking: thinking}
+		thinking, ok := m["thinking"].(string)
+		if !ok {
+			thinking = ""
+		}
+		return &canonical.ContentBlock{Type: "thinking", Thinking: thinking}, nil
 	case "redacted_thinking":
 		// 丢弃
-		return nil
+		return nil, nil
 	}
-	return nil
+	return nil, nil
 }
 
 // decodeTools 解码工具定义
@@ -232,7 +270,10 @@ func decodeToolChoice(toolChoice any) *canonical.ToolChoice {
 			return canonical.NewToolChoiceAny()
 		}
 	case map[string]any:
-		t, _ := v["type"].(string)
+		t, ok := v["type"].(string)
+		if !ok {
+			return nil
+		}
 		switch t {
 		case "auto":
 			return canonical.NewToolChoiceAuto()
@@ -241,7 +282,10 @@ func decodeToolChoice(toolChoice any) *canonical.ToolChoice {
 		case "any":
 			return canonical.NewToolChoiceAny()
 		case "tool":
-			name, _ := v["name"].(string)
+			name, ok := v["name"].(string)
+			if !ok {
+				name = ""
+			}
 			return canonical.NewToolChoiceNamed(name)
 		}
 	}