feat: 单插件重载等 PluginMgr 能力导出到外部 SDK

- meta: CORE_PLUGIN_RELOAD_ONE(48) / LIST_LOADED(49) / IS_DISABLED(50)
- sdk: PluginMgrAPI 接口(ReloadOne/ListLoadedPlugins/IsPluginDisabled) +
  PluginSDK.SetPluginMgrAPI/PluginMgr() 访问器
- plugindev 模板: dispatchPluginMgr 桥接注入,走 C ABI 48/49/50

meta/meta.go

@@ -99,4 +99,9 @@ const (
 	CoreSettingsDefs          = 43
 	CoreSettingsDump          = 44
 	CoreSettingsPlugins       = 45
+	CoreRegisterInputCh       = 46
+	CoreInjectInputSync       = 47
+	CorePluginReloadOne       = 48
+	CorePluginListLoaded      = 49
+	CorePluginIsDisabled      = 50
 )