feat: 侧边栏新增位置兼容模式，为 Windows 原生标题栏预留顶部空间

新增 SidebarPrefs.titleBarCompat 设置项（默认关闭）：开启后 toggle cluster
下移 40px、右侧面板内容从标题栏条带下方开始，避免被 Windows 无边框窗口
右上角的原生标题栏遮挡。底部面板不受影响。设置页「常规」新增一行开关，
zh/en 双语，读写下穿既有 settings 路由。测试覆盖 parsePrefs 回退、schema
默认值、设置页渲染与开关状态。

src/client/SideCardSection.tsx

@@ -660,6 +660,17 @@ export function SideCardSection({ store, service }: SideCardSectionProps) {
             onChange={(next) => { applyPref({ interceptOpenPath: next }) }}
           />
         </div>
+        <div className={css.row}>
+          <span className={css.rowText}>
+            <span className={css.title}>{t('settingsTitleBarTitle')}</span>
+            <span className={css.desc}>{t('settingsTitleBarDesc')}</span>
+          </span>
+          <Switch
+            label={t('settingsTitleBarTitle')}
+            checked={prefs.titleBarCompat}
+            onChange={(next) => { applyPref({ titleBarCompat: next }) }}
+          />
+        </div>
       </div>
 
       {/* 侧边栏内容: one small card per registered tab type in a responsive

src/client/Sidebar.tsx

@@ -167,6 +167,21 @@ export function Sidebar(props: { ctx: Context; store: SidebarStore }) {
     return () => { document.body.removeAttribute('data-dsh-sidebar-collapsed') }
   }, [collapsed])
 
+  // Position compatibility mode (titleBarCompat pref): Windows frameless
+  // windows draw the native title bar (minimize/maximize/close) at the
+  // window's top-right corner, OVER the web content. When the user enables
+  // the pref, the body attribute lets sidebar.module.css drop the toggle
+  // cluster below the strip and push the right panel's content below it.
+  // The attribute rides the snapshot's prefs, so flipping the setting
+  // re-renders and re-applies immediately; the cleanup removes it on
+  // unmount/boundary swap so a crashed sidebar never leaves it behind.
+  const titleBarCompat = snapshot.prefs.titleBarCompat
+  useEffect(() => {
+    if (titleBarCompat) document.body.setAttribute('data-dsh-title-bar-compat', '')
+    else document.body.removeAttribute('data-dsh-title-bar-compat')
+    return () => { document.body.removeAttribute('data-dsh-title-bar-compat') }
+  }, [titleBarCompat])
+
   /**
    * Bottom-panel merge on narrow viewports: whenever a session is current
    * while narrow (mount, session switch, or a desktop→narrow transition),

src/client/locales.ts

@@ -116,6 +116,8 @@ export const zh = {
   settingsWidthSuffix: '%',
   settingsOpenPathTitle: '聊天区文件在侧边栏打开',
   settingsOpenPathDesc: '在聊天里点击文件链接（工具行、产物列表、文件提及）时，在侧边栏编辑器中打开，不再调用系统默认应用',
+  settingsTitleBarTitle: '位置兼容模式',
+  settingsTitleBarDesc: '为 Windows 右上角的原生标题栏预留空间：侧边栏按钮与侧边栏内容整体下移，避免被标题栏遮挡',
   settingsSaveFailed: '保存失败',
   settingsConflict: '设置已被其他窗口修改，请重试',
   binaryNoPreview: '此文件类型不支持预览',
@@ -333,6 +335,8 @@ export const en: Record<keyof typeof zh, string> = {
   settingsWidthSuffix: '%',
   settingsOpenPathTitle: 'Open chat files in the sidebar',
   settingsOpenPathDesc: 'Open file links in the chat (tool rows, produced files, mentions) in the sidebar editor instead of the system default app',
+  settingsTitleBarTitle: 'Position compatibility mode',
+  settingsTitleBarDesc: 'Reserve space for the native Windows title bar at the top-right so the sidebar buttons and content sit below it instead of underneath',
   settingsSaveFailed: 'Failed to save',
   settingsConflict: 'The setting changed in another window — please retry',
   binaryNoPreview: 'This file type cannot be previewed',

src/client/prefs.ts

@@ -59,6 +59,9 @@ export function parsePrefs(value: unknown): SidebarPrefs {
     interceptOpenPath: typeof record.interceptOpenPath === 'boolean'
       ? record.interceptOpenPath
       : SIDEBAR_PREFS_DEFAULTS.interceptOpenPath,
+    titleBarCompat: typeof record.titleBarCompat === 'boolean'
+      ? record.titleBarCompat
+      : SIDEBAR_PREFS_DEFAULTS.titleBarCompat,
     htmlViewerNoSandbox: typeof record.htmlViewerNoSandbox === 'boolean'
       ? record.htmlViewerNoSandbox
       : SIDEBAR_PREFS_DEFAULTS.htmlViewerNoSandbox,

src/client/sidebar.module.css

@@ -209,6 +209,28 @@
   padding-right: 40px;
 }
 
+/* ── Position compatibility mode (Windows native title bar) ────────────── */
+
+/* Windows frameless / hidden-title-bar windows draw the native caption
+   strip (minimize / maximize / close) at the window's top-right corner,
+   OVER the web content. When the user enables the "position compatibility"
+   pref, the sidebar yields the strip: the toggle cluster drops below it and
+   the right panel's content starts below it — the panel's surface still
+   spans the full height, so the caption buttons float over empty sidebar
+   fill (the VSCode hidden-title-bar look). The bottom panel is unaffected:
+   it sits at the window's bottom, never under the top strip. The Sidebar
+   shell toggles the body attribute from the prefs. */
+:global(body[data-dsh-title-bar-compat]) .toggleCluster {
+  top: 43px; /* 40px caption strip + the original 3px inset */
+}
+
+:global(body[data-dsh-title-bar-compat]) .panel {
+  /* The caption strip is drawn over the panel's own top edge: keep the
+     surface full-height and push the content (the tab strip) below the
+     strip instead. .panelResize is absolutely positioned and unaffected. */
+  padding-top: 40px;
+}
+
 /* The shared corner (both panels open): the intersection of the right
    panel's left edge and the bottom panel's top edge. Horizontal drags
    resize the width, vertical drags the height — the two panels drag

src/config.ts

@@ -91,6 +91,7 @@ export const PrefsSchema: z<SidebarPrefs> = z.object({
   terminalFontFamily: z.string().default(''),
   terminalFontSize: z.number().step(1).min(TERMINAL_FONT_SIZE_MIN).max(TERMINAL_FONT_SIZE_MAX).default(TERMINAL_FONT_SIZE_DEFAULT),
   interceptOpenPath: z.boolean().default(true),
+  titleBarCompat: z.boolean().default(false),
   htmlViewerNoSandbox: z.boolean().default(false),
   htmlViewerDefaultUnsafe: z.boolean().default(false),
   browserNoSandbox: z.boolean().default(false),

src/prefs-shared.ts

@@ -60,6 +60,14 @@ export interface SidebarPrefs {
    * own enable switch gates it too (both must be on for the takeover).
    */
   interceptOpenPath: boolean
+  /**
+   * Position compatibility mode: reserves space at the top for the native
+   * Windows title bar (drawn at the window's top-right corner over the web
+   * content in frameless/hidden-title-bar windows). When on, the toggle
+   * cluster drops below the strip and the right panel's content starts
+   * below it. Off by default — the sidebar layout is untouched.
+   */
+  titleBarCompat: boolean
   /**
    * Whether the HTML previewer drops its sandboxed iframe. Sandbox ON (the
    * default) renders previewed HTML in an opaque-origin iframe that cannot
@@ -159,6 +167,7 @@ export const SIDEBAR_PREFS_DEFAULTS: SidebarPrefs = {
   terminalFontFamily: '',
   terminalFontSize: TERMINAL_FONT_SIZE_DEFAULT,
   interceptOpenPath: true,
+  titleBarCompat: false,
   htmlViewerNoSandbox: false,
   htmlViewerDefaultUnsafe: false,
   browserNoSandbox: false,