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/client/desktop-env.ts

@@ -1,21 +1,18 @@
 /**
- * Desktop-shell detection for the sidebar. The official DSH Desktop shell
- * (Electron) stamps every render URL with `dsh-desktop-mode` and
- * `dsh-desktop-platform` and exposes `window.__DSH_DESKTOP_FILE_PATH__`
- * through its preload; community Tauri shells keep the native system frame
- * (no stamps — plain-browser semantics). Parsed once per page and memoized
- * (the URL never changes mid-session); `resetDesktopEnvForTests` clears the
- * memo for unit tests.
+ * Desktop-shell detection for the sidebar. Shells may stamp the render URL
+ * with `dsh-desktop-mode` / `dsh-desktop-platform` (the official Electron
+ * shell does) and expose `window.__DSH_DESKTOP_FILE_PATH__` through a
+ * preload. Parsed once per page and memoized (the URL never changes
+ * mid-session); `resetDesktopEnvForTests` clears the memo for unit tests.
  *
- * Geometry facts the sidebar adapts to (from the Electron runtime):
- * - win32 `advanced` mode draws the window controls in a 32px overlay strip
- *   at the top-right of the web content (`titleBarOverlay: { height: 32 }`)
- *   — exactly where the toggle cluster sits, so it must drop below the
- *   strip and the right panel's content must clear it.
- * - darwin `advanced` mode keeps the traffic lights at (16,16) in the
- *   top-left; nothing on the plugin's side touches that corner today, but
- *   the platform is still reported so left-edge controls can avoid it.
- * - `compatibility` mode keeps the native frame — no adaptation needed.
+ * GEOMETRY POLICY: this module only REPORTS shell facts — it never decides
+ * how to adapt. The strip height comes from standard signals first (the
+ * Window Controls Overlay API, see wco.ts), then the documented contract
+ * parameter `dsh-desktop-titlebar-inset` (a shell may stamp the real pixels
+ * it reserves at the top), then the user's chosen scheme (preset / custom).
+ * The legacy win32-advanced 32px constant is gone from the core: it lives
+ * in the opt-in shell preset (shell-presets.ts) as a fallback for shells
+ * without the WCO API.
  */
 export interface DesktopEnv {
   /** Running inside a desktop shell (any URL stamp or preload marker). */
@@ -24,34 +21,51 @@ export interface DesktopEnv {
   readonly mode: 'compatibility' | 'advanced' | null
   /** Shell platform stamp ('darwin' | 'win32' | …), lowercased, or null. */
   readonly platform: string | null
-  /** Pixels the win32 advanced shell reserves at the top-right for window
-   *  controls (0 elsewhere). */
-  readonly win32OverlayTop: number
+  /**
+   * Contract parameter `dsh-desktop-titlebar-inset`: pixels the shell
+   * reserves at the top of the web content for its own chrome (0–120,
+   * clamped; 0 when absent). Standard WCO geometry takes precedence over
+   * this whenever the API is available.
+   */
+  readonly titlebarInset: number
 }
 
 let cached: DesktopEnv | undefined
 
-/** Read the shell's desktop stamps (memoized per page). */
+/** Read the shell's desktop stamps (memoized per page; SSR-safe). */
 export function parseDesktopEnv(): DesktopEnv {
   if (cached !== undefined) return cached
+  const hasWindow = typeof window !== 'undefined'
+  const hasPreloadMarker = hasWindow
+    && typeof (window as { __DSH_DESKTOP_FILE_PATH__?: unknown }).__DSH_DESKTOP_FILE_PATH__ !== 'undefined'
   // location.search includes the leading '?', which URLSearchParams does NOT
   // strip (it would become part of the first key) — drop it explicitly.
-  const params = new URLSearchParams(window.location.search.replace(/^\?/, ''))
+  // SSR (no window) resolves the empty environment: nothing desktop.
+  const params = hasWindow
+    ? new URLSearchParams(window.location.search.replace(/^\?/, ''))
+    : new URLSearchParams()
   const modeParam = params.get('dsh-desktop-mode')
   const mode = modeParam === 'compatibility' || modeParam === 'advanced' ? modeParam : null
   const platformParam = params.get('dsh-desktop-platform')
   const platform = platformParam !== null && platformParam !== '' ? platformParam.toLowerCase() : null
-  const desktop = mode !== null
-    || typeof (window as { __DSH_DESKTOP_FILE_PATH__?: unknown }).__DSH_DESKTOP_FILE_PATH__ !== 'undefined'
+  const desktop = mode !== null || hasPreloadMarker
   cached = {
     desktop,
     mode,
     platform,
-    win32OverlayTop: desktop && mode === 'advanced' && platform === 'win32' ? 32 : 0,
+    titlebarInset: parseTitlebarInset(params.get('dsh-desktop-titlebar-inset')),
   }
   return cached
 }
 
+/** Clamp the contract inset parameter into 0–120 (invalid/absent → 0). */
+function parseTitlebarInset(raw: string | null): number {
+  if (raw === null) return 0
+  const parsed = Number(raw)
+  if (!Number.isFinite(parsed)) return 0
+  return Math.min(120, Math.max(0, Math.round(parsed)))
+}
+
 /** Test hook: drop the memo so the next parse re-reads the URL/globals. */
 export function resetDesktopEnvForTests(): void {
   cached = undefined