docs(readme): declare the native sidebar API adaptation at the top

A GFM IMPORTANT alert under the title states that the right column is
DSH's own sidebar since v0.19.0 (tab types/bodies via ctx.sidebarRightTabs
/ ctx.sidebarRight, file opens via ctx.sidebarRight.openResource, no
self-drawn right panel), and that the bottom workbench plus the
ctx.betterSidebar service are unchanged.

README.md

@@ -1,5 +1,8 @@
 # dsh-better-sidebar
 
+> [!IMPORTANT]
+> **已适配 DSH 原生侧边栏 API**（v0.19.0 起，DSH `0.1.5-rc.1+`）：右列就是 DSH 自己的右侧栏——插件的每个 tab 类型与 tab 体通过 `ctx.sidebarRightTabs` / `ctx.sidebarRight` 注册与打开，聊天里的文件打开统一走 `ctx.sidebarRight.openResource('dsh-resource://file/…')`，插件**不再自绘右侧面板**（旧的浮窗能力同步移除）。自绘的底部工作台与开放给其他插件的 `ctx.betterSidebar` 服务保持不变，接入方式见[插件接入指南](docs/external-plugin-guide.md)。
+
 <!-- Hero -->
 <div align="center">
   <b style="font-size: 1.15em;">一个服务化的侧边栏框架，一套开箱即用的完整工作台</b><br /><br />

README_EN.md

@@ -1,5 +1,8 @@
 # dsh-better-sidebar
 
+> [!IMPORTANT]
+> **Built on DSH's native sidebar API** (since v0.19.0, DSH `0.1.5-rc.1+`): the right column *is* DSH's own sidebar — every plugin tab type and tab body registers and opens through `ctx.sidebarRightTabs` / `ctx.sidebarRight`, every file open from the chat goes through `ctx.sidebarRight.openResource('dsh-resource://file/…')`, and the plugin **no longer draws a right panel of its own** (the old free-window capability is gone with it). The self-drawn bottom workbench and the `ctx.betterSidebar` service other plugins register against are unchanged — see the [plugin integration guide](docs/external-plugin-guide.md).
+
 <!-- Hero -->
 <div align="center">
   <b style="font-size: 1.15em;">A service-oriented sidebar framework, and a complete workbench out of the box</b><br /><br />