feat: ConfigRegistry + SettingsAPI for plugin config access

Core exposes a unified settings interface through Plugin SDK:
- internal/config/registry.go: thread-safe namespaced KV store
  - Register/Get/Set/List/Delete with JSON persistence
  - Flush() for explicit save to disk
- SettingsAPI in SDK: plugins call plugin.Settings().Get/Set/List
  - Full access: read/write any key (core.*, plugin.<name>.*)
- plugin.Registry.SetConfigRegistry() wires it into SDK plugins
- main.go registers core.* keys at startup, flushes on shutdown
- 7 tests for ConfigRegistry

internal/plugin/plugin.go

@@ -12,6 +12,7 @@ import (
 	"time"
 
 	agentIO "gitcode.com/JianFeeeee/HomeAgent/internal/agent/io"
+	internalConfig "gitcode.com/JianFeeeee/HomeAgent/internal/config"
 	sdk "gitcode.com/JianFeeeee/HomeAgent/internal/plugin/sdk"
 )
 
@@ -149,6 +150,14 @@ type Registry struct {
 	ioMgr     *agentIO.IOManager
 	factories map[string]NativeFactory // 名称匹配的插件使用原生实现
 	sdkAPIs   map[string]*sdkAPI       // SDK 插件 API 实例
+	cfgReg    *internalConfig.ConfigRegistry
+}
+
+// SetConfigRegistry 注入全局配置注册表，使 SDK 插件可访问配置
+func (r *Registry) SetConfigRegistry(cr *internalConfig.ConfigRegistry) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	r.cfgReg = cr
 }
 
 type sdkAPI struct {
@@ -172,6 +181,15 @@ func (r *Registry) RegisterPluginAPI(api *sdk.PluginAPI) error {
 	if _, ok := r.sdkAPIs[api.Name]; ok {
 		return fmt.Errorf("sdk api %s already registered", api.Name)
 	}
+
+	// 注入 SettingsAPI（读取/修改核心与其他插件配置）
+	if r.cfgReg != nil {
+		api.SetSettings(&pluginSettings{
+			reg:  r.cfgReg,
+			name: api.Name,
+		})
+	}
+
 	r.sdkAPIs[api.Name] = &sdkAPI{
 		api:    api,
 		tools:  api.Tools(),
@@ -187,6 +205,24 @@ func (r *Registry) RegisterPluginAPI(api *sdk.PluginAPI) error {
 	return nil
 }
 
+// pluginSettings 实现 SettingsAPI，以插件名为命名空间
+type pluginSettings struct {
+	reg  *internalConfig.ConfigRegistry
+	name string
+}
+
+func (s *pluginSettings) Get(key string) (interface{}, error) {
+	return s.reg.Get(key)
+}
+
+func (s *pluginSettings) Set(key string, value interface{}) error {
+	return s.reg.Set(key, value)
+}
+
+func (s *pluginSettings) List(prefix string) ([]string, error) {
+	return s.reg.List(prefix), nil
+}
+
 // GetAllSDKToolDefs 收集所有 SDK 插件的工具定义
 func (r *Registry) GetAllSDKToolDefs() []sdk.ToolDef {
 	r.mu.RLock()