feat: 实现完整的本地配置管理与CLI重构

本次重构实现了标准化的本地配置系统，替换原有的硬编码环境变量读取逻辑：
1. 新增跨平台的原子化配置文件读写，支持Unix和Windows系统
2. 新增init命令用于安全初始化和更新本地凭据
3. 替换原有错误提示文案为更友好的中文提示
4. 更新文档说明新的配置流程和安全规范
5. 新增完整的配置相关测试用例
6. 添加必要的依赖包支持

internal/command/init_test.go

@@ -0,0 +1,60 @@
+package command
+
+import (
+	"bytes"
+	"encoding/json"
+	"io"
+	"strings"
+	"testing"
+)
+
+func TestInitCommandReadsTokenWithoutPrintingIt(t *testing.T) {
+	const token = "test-private-token"
+	var receivedToken string
+	cmd := newInitCommand(
+		func(value string) (string, error) {
+			receivedToken = value
+			return "/test/repository/.env", nil
+		},
+		func(input io.Reader, output io.Writer) (string, error) {
+			_, _ = io.WriteString(output, "credential prompt")
+			return token, nil
+		},
+	)
+	var stdout, stderr bytes.Buffer
+	cmd.SetOut(&stdout)
+	cmd.SetErr(&stderr)
+	if err := cmd.Execute(); err != nil {
+		t.Fatal(err)
+	}
+	if receivedToken != token {
+		t.Fatalf("initializer received token=%q", receivedToken)
+	}
+	if strings.Contains(stdout.String(), token) || strings.Contains(stderr.String(), token) {
+		t.Fatal("init output exposed the token")
+	}
+	result := initResult{}
+	if err := json.Unmarshal(stdout.Bytes(), &result); err != nil {
+		t.Fatalf("decode init result: %v", err)
+	}
+	if !result.Initialized || result.EnvFile != "/test/repository/.env" {
+		t.Fatalf("result = %#v", result)
+	}
+}
+
+func TestInitCommandDoesNotExposeForceFlag(t *testing.T) {
+	cmd := newInitCommand(func(string) (string, error) {
+		return "", nil
+	}, func(io.Reader, io.Writer) (string, error) {
+		return "token", nil
+	})
+	if cmd.Flags().Lookup("force") != nil {
+		t.Fatal("init still exposes the retired --force flag")
+	}
+}
+
+func TestInitTerminalReaderRejectsNonTTY(t *testing.T) {
+	if _, err := readTokenFromTerminal(bytes.NewBufferString("token\n"), io.Discard); err == nil || !strings.Contains(err.Error(), "交互式终端") {
+		t.Fatalf("error = %v", err)
+	}
+}