feat(sidebar): 桌面兼容三方案——自动检测(WCO 标准几何)/壳预设/自定义 CSS (#284)

* feat(sidebar): 桌面兼容三方案——自动检测(WCO 标准几何)/壳预设/自定义 CSS

核心只保留 Web 标准机制，壳专属适配全部下沉到用户空间（KISS）：
- prefs 新增 titleBarScheme(默认 auto)/titleBarPresetId/customCss，旧 titleBarCompat
  布尔自动迁移（true→custom 保留 stripPx，false/缺失→auto）
- wco.ts：navigator.windowControlsOverlay 反应式几何（geometrychange 实时更新；
  visible=false 的幽灵 API 视为缺失），实现 #257
- titlebar-strip.ts 唯一 strip 取值链：WCO → dsh-desktop-titlebar-inset 契约参数
  → 预设 stripFor → 手动 px → 0；desktop-env.ts 移除 win32 32px 硬编码
- shell-presets.ts 数据驱动预设（准入：issue/PR 提及 + 100+ star；v1 仅
  anywhere-labs DSH Desktop：darwin 20px / win32 无 WCO 时 32px），opt-in 手动
- 预设/自定义 CSS 注入（data-dsh-preset-css / data-dsh-custom-css 标签），
  chrome 补稳定寻址面 data-dsh-toggle-cluster / data-dsh-panel
- 交互 chrome 统一 -webkit-app-region: no-drag（吸收 #111/#153）
- layout.css 底栏推挤复合锚点（[data-pane] 与 :has(> [data-slot]) 双保险，
  rc.8 实测前者失效、后者命中，吸收 #226 思路）
- 设置 UI：位置兼容模式齿轮弹窗改三方案（自动检测/壳兼容方案/自定义方案）
- 测试：wco/titlebar-strip/shell-presets 单测 + prefs 迁移 + e2e 5 场景
  （保守 auto/WCO 反应式/预设/自定义 CSS/复合锚点），挂载门禁 12/12 全绿

核心 grep 无壳专属类名；为某壳做的兼容在另一壳会再坏——预设与自定义 CSS
是唯一出路（AGENTS.md §8 契约已更新）。

* refine(sidebar): 位置兼容模式改主行下拉四选项——自动检测/DSH官方Web/壳预设/自定义

按用户反馈定稿 UI：
- 主行下拉：自动检测（默认）/ DSH官方Web（显式零适配，连 WCO 也强制 0）/
  各壳预设（命中环境带「已检测」后缀，仅提示）/ 自定义方案（保留齿轮弹窗：
  下移距离 + 自定义 CSS）
- 旧文档迁移：titleBarCompat=true 或 titleBarStripPx 非默认值（此前已有配置）
  → 默认落到 custom 方案保留用户数值；干净文档 → auto
- prefs 新增 'web' 方案；strip 取值链最优先处理 web→0
- 测试：prefs 迁移（stripPx 48→custom / 40→auto）、web 强制 0、下拉渲染断言
- 单测 693 通过，挂载 e2e 12/12 全绿

* refine(sidebar): 方案下拉复用 SelectMenu 组件，不用原生 <select>

- 抽出可复用 SelectMenu（primitives Menu：锚点按钮 + 下拉选项卡，支持
  icon/desc/多选），SelectRow 改为其薄壳
- 位置兼容模式方案下拉改用 SelectMenu；选项带描述（自动检测/DSH官方Web/
  各壳预设(命中带「已检测」后缀)/自定义方案）
- 移除原生 select 样式；单测 693 通过，挂载 e2e 12/12 全绿

src/prefs-shared.ts

@@ -85,17 +85,43 @@ export interface SidebarPrefs {
    */
   terminalShellArgs: string
   /**
-   * 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.
+   * Title-bar / shell compatibility scheme (the "位置兼容模式" setting):
+   * - `auto` (default): CONSERVATIVE — only the standard Window Controls
+   *   Overlay API (present in frameless Chromium shells that draw the
+   *   native caption buttons over web content) contributes real geometry;
+   *   without it nothing is modified, so plain-browser (web) behavior is
+   *   untouched.
+   * - `web`: EXPLICIT "DSH official web" — never adapt, not even WCO
+   *   geometry (the user declares they run the plain web UI).
+   * - `preset`: apply the built-in shell preset named by
+   *   `titleBarPresetId` (data-driven, opt-in — see shell-presets.ts).
+   * - `custom`: apply the free-form `customCss` (and the legacy
+   *   `titleBarStripPx` strip).
+   */
+  titleBarScheme: TitleBarScheme
+  /**
+   * The built-in shell preset id applied while `titleBarScheme` is
+   * `preset` ('' = no preset — nothing extra is applied).
+   */
+  titleBarPresetId: string
+  /**
+   * Free-form CSS injected into the page (last in the cascade, so it can
+   * override the plugin's styles; use `!important` to override JS-written
+   * inline CSS variables). Applied while `titleBarScheme` is `custom`.
+   */
+  customCss: string
+  /**
+   * LEGACY (kept for read-migration and downgrade mirroring only): position
+   * compatibility mode flag. The UI writes `titleBarScheme` instead; a
+   * stored `true` without a scheme migrates to the `custom` scheme (with
+   * `titleBarStripPx` preserved).
    */
   titleBarCompat: boolean
   /**
-   * The reserved top strip height in px when `titleBarCompat` is on
-   * (0–120, default 40). Drives the `--dsh-title-bar-strip` CSS variable:
-   * the toggle cluster drops `strip + 3px` and the right panel's content
+   * LEGACY (kept for read-migration and downgrade mirroring only): the
+   * reserved top strip height in px used by the `custom` scheme (0–120,
+   * default 40). Drives the `--dsh-title-bar-strip` CSS variable: the
+   * toggle cluster drops `strip + 3px` and the right panel's content
    * starts `strip` px below its top edge.
    */
   titleBarStripPx: number
@@ -192,6 +218,10 @@ export const TITLE_BAR_STRIP_MIN = 0
 export const TITLE_BAR_STRIP_MAX = 120
 export const TITLE_BAR_STRIP_DEFAULT = 40
 
+/** The title-bar / shell compatibility schemes (see {@link SidebarPrefs.titleBarScheme}). */
+export const TITLE_BAR_SCHEMES = ['auto', 'web', 'preset', 'custom'] as const
+export type TitleBarScheme = typeof TITLE_BAR_SCHEMES[number]
+
 /** Fallback prefs used whenever the settings document is unreachable or malformed. */
 export const SIDEBAR_PREFS_DEFAULTS: SidebarPrefs = {
   openByDefault: false,
@@ -206,6 +236,9 @@ export const SIDEBAR_PREFS_DEFAULTS: SidebarPrefs = {
   editorExplorer: false,
   terminalShell: '',
   terminalShellArgs: '',
+  titleBarScheme: 'auto',
+  titleBarPresetId: '',
+  customCss: '',
   titleBarCompat: false,
   titleBarStripPx: TITLE_BAR_STRIP_DEFAULT,
   htmlViewerNoSandbox: false,