docs(sdk-access): add SDK usage guides in English and Chinese

- Added `sdk-access.md` and `sdk-access_CN.md` documentation files.
- Included detailed guidelines for authentication manager lifecycle, configuration, built-in and custom providers.
- Documented integration steps with `cliproxy` and instructions for hot reloading.

docs/sdk-access.md

@@ -0,0 +1,176 @@
+# @sdk/access SDK Reference
+
+The `github.com/router-for-me/CLIProxyAPI/v6/sdk/access` package centralizes inbound request authentication for the proxy. It offers a lightweight manager that chains credential providers, so servers can reuse the same access control logic inside or outside the CLI runtime.
+
+## Importing
+
+```go
+import (
+    sdkaccess "github.com/router-for-me/CLIProxyAPI/v6/sdk/access"
+    "github.com/router-for-me/CLIProxyAPI/v6/internal/config"
+)
+```
+
+Add the module with `go get github.com/router-for-me/CLIProxyAPI/v6/sdk/access`.
+
+## Manager Lifecycle
+
+```go
+manager := sdkaccess.NewManager()
+providers, err := sdkaccess.BuildProviders(cfg)
+if err != nil {
+    return err
+}
+manager.SetProviders(providers)
+```
+
+* `NewManager` constructs an empty manager.
+* `SetProviders` replaces the provider slice using a defensive copy.
+* `Providers` retrieves a snapshot that can be iterated safely from other goroutines.
+* `BuildProviders` translates `config.Config` access declarations into runnable providers. When the config omits explicit providers but defines inline API keys, the helper auto-installs the built-in `config-api-key` provider.
+
+## Authenticating Requests
+
+```go
+result, err := manager.Authenticate(ctx, req)
+switch {
+case err == nil:
+    // Authentication succeeded; result describes the provider and principal.
+case errors.Is(err, sdkaccess.ErrNoCredentials):
+    // No recognizable credentials were supplied.
+case errors.Is(err, sdkaccess.ErrInvalidCredential):
+    // Supplied credentials were present but rejected.
+default:
+    // Transport-level failure was returned by a provider.
+}
+```
+
+`Manager.Authenticate` walks the configured providers in order. It returns on the first success, skips providers that surface `ErrNotHandled`, and tracks whether any provider reported `ErrNoCredentials` or `ErrInvalidCredential` for downstream error reporting.
+
+If the manager itself is `nil` or no providers are registered, the call returns `nil, nil`, allowing callers to treat access control as disabled without branching on errors.
+
+Each `Result` includes the provider identifier, the resolved principal, and optional metadata (for example, which header carried the credential).
+
+## Configuration Layout
+
+The manager expects access providers under the `auth.providers` key inside `config.yaml`:
+
+```yaml
+auth:
+  providers:
+    - name: inline-api
+      type: config-api-key
+      api-keys:
+        - sk-test-123
+        - sk-prod-456
+```
+
+Fields map directly to `config.AccessProvider`: `name` labels the provider, `type` selects the registered factory, `sdk` can name an external module, `api-keys` seeds inline credentials, and `config` passes provider-specific options.
+
+### Loading providers from external SDK modules
+
+To consume a provider shipped in another Go module, point the `sdk` field at the module path and import it for its registration side effect:
+
+```yaml
+auth:
+  providers:
+    - name: partner-auth
+      type: partner-token
+      sdk: github.com/acme/xplatform/sdk/access/providers/partner
+      config:
+        region: us-west-2
+        audience: cli-proxy
+```
+
+```go
+import (
+    _ "github.com/acme/xplatform/sdk/access/providers/partner" // registers partner-token
+    sdkaccess "github.com/router-for-me/CLIProxyAPI/v6/sdk/access"
+)
+```
+
+The blank identifier import ensures `init` runs so `sdkaccess.RegisterProvider` executes before `BuildProviders` is called.
+
+## Built-in Providers
+
+The SDK ships with one provider out of the box:
+
+- `config-api-key`: Validates API keys declared inline or under top-level `api-keys`. It accepts the key from `Authorization: Bearer`, `X-Goog-Api-Key`, `X-Api-Key`, or the `?key=` query string and reports `ErrInvalidCredential` when no match is found.
+
+Additional providers can be delivered by third-party packages. When a provider package is imported, it registers itself with `sdkaccess.RegisterProvider`.
+
+### Metadata and auditing
+
+`Result.Metadata` carries provider-specific context. The built-in `config-api-key` provider, for example, stores the credential source (`authorization`, `x-goog-api-key`, `x-api-key`, or `query-key`). Populate this map in custom providers to enrich logs and downstream auditing.
+
+## Writing Custom Providers
+
+```go
+type customProvider struct{}
+
+func (p *customProvider) Identifier() string { return "my-provider" }
+
+func (p *customProvider) Authenticate(ctx context.Context, r *http.Request) (*sdkaccess.Result, error) {
+    token := r.Header.Get("X-Custom")
+    if token == "" {
+        return nil, sdkaccess.ErrNoCredentials
+    }
+    if token != "expected" {
+        return nil, sdkaccess.ErrInvalidCredential
+    }
+    return &sdkaccess.Result{
+        Provider:  p.Identifier(),
+        Principal: "service-user",
+        Metadata:  map[string]string{"source": "x-custom"},
+    }, nil
+}
+
+func init() {
+    sdkaccess.RegisterProvider("custom", func(cfg *config.AccessProvider, root *config.Config) (sdkaccess.Provider, error) {
+        return &customProvider{}, nil
+    })
+}
+```
+
+A provider must implement `Identifier()` and `Authenticate()`. To expose it to configuration, call `RegisterProvider` inside `init`. Provider factories receive the specific `AccessProvider` block plus the full root configuration for contextual needs.
+
+## Error Semantics
+
+- `ErrNoCredentials`: no credentials were present or recognized by any provider.
+- `ErrInvalidCredential`: at least one provider processed the credentials but rejected them.
+- `ErrNotHandled`: instructs the manager to fall through to the next provider without affecting aggregate error reporting.
+
+Return custom errors to surface transport failures; they propagate immediately to the caller instead of being masked.
+
+## Integration with cliproxy Service
+
+`sdk/cliproxy` wires `@sdk/access` automatically when you build a CLI service via `cliproxy.NewBuilder`. Supplying a preconfigured manager allows you to extend or override the default providers:
+
+```go
+coreCfg, _ := config.LoadConfig("config.yaml")
+providers, _ := sdkaccess.BuildProviders(coreCfg)
+manager := sdkaccess.NewManager()
+manager.SetProviders(providers)
+
+svc, _ := cliproxy.NewBuilder().
+  WithConfig(coreCfg).
+  WithAccessManager(manager).
+  Build()
+```
+
+The service reuses the manager for every inbound request, ensuring consistent authentication across embedded deployments and the canonical CLI binary.
+
+### Hot reloading providers
+
+When configuration changes, rebuild providers and swap them into the manager:
+
+```go
+providers, err := sdkaccess.BuildProviders(newCfg)
+if err != nil {
+    log.Errorf("reload auth providers failed: %v", err)
+    return
+}
+accessManager.SetProviders(providers)
+```
+
+This mirrors the behaviour in `cliproxy.Service.refreshAccessProviders` and `api.Server.applyAccessConfig`, enabling runtime updates without restarting the process.

docs/sdk-access_CN.md

@@ -0,0 +1,176 @@
+# @sdk/access 开发指引
+
+`github.com/router-for-me/CLIProxyAPI/v6/sdk/access` 包负责代理的入站访问认证。它提供一个轻量的管理器，用于按顺序链接多种凭证校验实现，让服务器在 CLI 运行时内外都能复用相同的访问控制逻辑。
+
+## 引用方式
+
+```go
+import (
+    sdkaccess "github.com/router-for-me/CLIProxyAPI/v6/sdk/access"
+    "github.com/router-for-me/CLIProxyAPI/v6/internal/config"
+)
+```
+
+通过 `go get github.com/router-for-me/CLIProxyAPI/v6/sdk/access` 添加依赖。
+
+## 管理器生命周期
+
+```go
+manager := sdkaccess.NewManager()
+providers, err := sdkaccess.BuildProviders(cfg)
+if err != nil {
+    return err
+}
+manager.SetProviders(providers)
+```
+
+- `NewManager` 创建空管理器。
+- `SetProviders` 替换提供者切片并做防御性拷贝。
+- `Providers` 返回适合并发读取的快照。
+- `BuildProviders` 将 `config.Config` 中的访问配置转换成可运行的提供者。当配置没有显式声明但包含顶层 `api-keys` 时，会自动挂载内建的 `config-api-key` 提供者。
+
+## 认证请求
+
+```go
+result, err := manager.Authenticate(ctx, req)
+switch {
+case err == nil:
+    // Authentication succeeded; result carries provider and principal.
+case errors.Is(err, sdkaccess.ErrNoCredentials):
+    // No recognizable credentials were supplied.
+case errors.Is(err, sdkaccess.ErrInvalidCredential):
+    // Credentials were present but rejected.
+default:
+    // Provider surfaced a transport-level failure.
+}
+```
+
+`Manager.Authenticate` 按配置顺序遍历提供者。遇到成功立即返回，`ErrNotHandled` 会继续尝试下一个；若发现 `ErrNoCredentials` 或 `ErrInvalidCredential`，会在遍历结束后汇总给调用方。
+
+若管理器本身为 `nil` 或尚未注册提供者，调用会返回 `nil, nil`，让调用方无需针对错误做额外分支即可关闭访问控制。
+
+`Result` 提供认证提供者标识、解析出的主体以及可选元数据（例如凭证来源）。
+
+## 配置结构
+
+在 `config.yaml` 的 `auth.providers` 下定义访问提供者：
+
+```yaml
+auth:
+  providers:
+    - name: inline-api
+      type: config-api-key
+      api-keys:
+        - sk-test-123
+        - sk-prod-456
+```
+
+条目映射到 `config.AccessProvider`：`name` 指定实例名，`type` 选择注册的工厂，`sdk` 可引用第三方模块，`api-keys` 提供内联凭证，`config` 用于传递特定选项。
+
+### 引入外部 SDK 提供者
+
+若要消费其它 Go 模块输出的访问提供者，可在配置里填写 `sdk` 字段并在代码中引入该包，利用其 `init` 注册过程：
+
+```yaml
+auth:
+  providers:
+    - name: partner-auth
+      type: partner-token
+      sdk: github.com/acme/xplatform/sdk/access/providers/partner
+      config:
+        region: us-west-2
+        audience: cli-proxy
+```
+
+```go
+import (
+    _ "github.com/acme/xplatform/sdk/access/providers/partner" // registers partner-token
+    sdkaccess "github.com/router-for-me/CLIProxyAPI/v6/sdk/access"
+)
+```
+
+通过空白标识符导入即可确保 `init` 调用，先于 `BuildProviders` 完成 `sdkaccess.RegisterProvider`。
+
+## 内建提供者
+
+当前 SDK 默认内置：
+
+- `config-api-key`：校验配置中的 API Key。它从 `Authorization: Bearer`、`X-Goog-Api-Key`、`X-Api-Key` 以及查询参数 `?key=` 提取凭证，不匹配时抛出 `ErrInvalidCredential`。
+
+导入第三方包即可通过 `sdkaccess.RegisterProvider` 注册更多类型。
+
+### 元数据与审计
+
+`Result.Metadata` 用于携带提供者特定的上下文信息。内建的 `config-api-key` 会记录凭证来源（`authorization`、`x-goog-api-key`、`x-api-key` 或 `query-key`）。自定义提供者同样可以填充该 Map，以便丰富日志与审计场景。
+
+## 编写自定义提供者
+
+```go
+type customProvider struct{}
+
+func (p *customProvider) Identifier() string { return "my-provider" }
+
+func (p *customProvider) Authenticate(ctx context.Context, r *http.Request) (*sdkaccess.Result, error) {
+    token := r.Header.Get("X-Custom")
+    if token == "" {
+        return nil, sdkaccess.ErrNoCredentials
+    }
+    if token != "expected" {
+        return nil, sdkaccess.ErrInvalidCredential
+    }
+    return &sdkaccess.Result{
+        Provider:  p.Identifier(),
+        Principal: "service-user",
+        Metadata:  map[string]string{"source": "x-custom"},
+    }, nil
+}
+
+func init() {
+    sdkaccess.RegisterProvider("custom", func(cfg *config.AccessProvider, root *config.Config) (sdkaccess.Provider, error) {
+        return &customProvider{}, nil
+    })
+}
+```
+
+自定义提供者需要实现 `Identifier()` 与 `Authenticate()`。在 `init` 中调用 `RegisterProvider` 暴露给配置层，工厂函数既能读取当前条目，也能访问完整根配置。
+
+## 错误语义
+
+- `ErrNoCredentials`：任何提供者都未识别到凭证。
+- `ErrInvalidCredential`：至少一个提供者处理了凭证但判定无效。
+- `ErrNotHandled`：告诉管理器跳到下一个提供者，不影响最终错误统计。
+
+自定义错误（例如网络异常）会马上冒泡返回。
+
+## 与 cliproxy 集成
+
+使用 `sdk/cliproxy` 构建服务时会自动接入 `@sdk/access`。如果需要扩展内置行为，可传入自定义管理器：
+
+```go
+coreCfg, _ := config.LoadConfig("config.yaml")
+providers, _ := sdkaccess.BuildProviders(coreCfg)
+manager := sdkaccess.NewManager()
+manager.SetProviders(providers)
+
+svc, _ := cliproxy.NewBuilder().
+  WithConfig(coreCfg).
+  WithAccessManager(manager).
+  Build()
+```
+
+服务会复用该管理器处理每一个入站请求，实现与 CLI 二进制一致的访问控制体验。
+
+### 动态热更新提供者
+
+当配置发生变化时，可以重新构建提供者并替换当前列表：
+
+```go
+providers, err := sdkaccess.BuildProviders(newCfg)
+if err != nil {
+    log.Errorf("reload auth providers failed: %v", err)
+    return
+}
+accessManager.SetProviders(providers)
+```
+
+这一流程与 `cliproxy.Service.refreshAccessProviders` 和 `api.Server.applyAccessConfig` 保持一致，避免为更新访问策略而重启进程。