test(i18n): add user-visible localization ratchet

docs/usage/configuration.en.md

@@ -4,6 +4,18 @@
 
 This page is split out from the [README](../../README.en.md) as the main ST-BME user configuration reference, preserving setting names, defaults, and tables for quick lookup by feature.
 
+### Interface language
+
+`Interface Language` only affects ST-BME frontend UI: the panel, menu entries, floating button, status messages, Toasts, recall cards, and graph system labels.
+
+Options:
+
+- `Auto`: follows the SillyTavern / browser language when available, otherwise falls back to Chinese.
+- `Simplified Chinese`: forces the Chinese UI.
+- `English`: forces the English UI.
+
+This setting **does not** translate chat content, user input, AI replies, memory nodes, recall injection text, or prompt construction. Switching the interface language does not change the memory graph or model behavior.
+
 ### Memory LLM
 
 The memory LLM is used for:

docs/usage/configuration.md

@@ -4,6 +4,18 @@
 
 本文从 [README](../../README.md) 拆出 ST-BME 的主要用户配置说明，保留设置名称、默认值和表格，便于按功能查阅。
 
+### 界面语言
+
+`界面语言` 只影响 ST-BME 前端 UI：面板、菜单入口、悬浮按钮、状态、Toast、召回卡片和图谱系统标签。
+
+可选值：
+
+- `自动`：优先跟随 SillyTavern / 浏览器语言，识别不到时使用中文。
+- `简体中文`：固定中文界面。
+- `English`：固定英文界面。
+
+这个设置**不会**翻译聊天内容、用户输入、AI 回复、记忆节点、召回注入文本或提示词构建。切换语言不会改变记忆图谱和模型行为。
+
 ### 记忆 LLM
 
 记忆 LLM 用于：