docs(readme): add WebView2 runtime note

.trellis/tasks/04-20-04-20-readme-webview2-note/task.json

@@ -0,0 +1,53 @@
+{
+  "id": "04-20-readme-webview2-note",
+  "name": "04-20-readme-webview2-note",
+  "title": "Add WebView2 runtime note to bilingual README",
+  "description": "Add Windows desktop runtime note to README.md and README_EN.md",
+  "status": "planning",
+  "dev_type": null,
+  "scope": null,
+  "package": null,
+  "priority": "P3",
+  "creator": "OpenCode",
+  "assignee": "OpenCode",
+  "createdAt": "2026-04-20",
+  "completedAt": null,
+  "branch": null,
+  "base_branch": "master",
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+      "action": "brainstorm"
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+    {
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+      "action": "research"
+    },
+    {
+      "phase": 3,
+      "action": "implement"
+    },
+    {
+      "phase": 4,
+      "action": "check"
+    },
+    {
+      "phase": 5,
+      "action": "update-spec"
+    },
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+      "action": "record-session"
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+  "subtasks": [],
+  "children": [],
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+  "relatedFiles": [],
+  "notes": "",
+  "meta": {}
+}

README.md

@@ -87,6 +87,13 @@ Windows 下默认产物路径：
 build/bin/ocswitch-desktop.exe
 ```
 
+提示：
+
+- Windows 11 一般已内置 WebView2 Runtime；主流 Windows 10 设备通常也已经安装。
+- `ocswitch-desktop.exe` 按单文件产物分发，不需要额外同目录依赖文件。
+- 如果桌面应用在 Windows 上无法启动，常见原因之一是系统缺少 WebView2 Runtime；这时请先安装 Microsoft Edge WebView2 Runtime 再重试：
+  https://developer.microsoft.com/microsoft-edge/webview2/
+
 ### 开发模式
 
 如果你想本地调试桌面 GUI：

README_EN.md

@@ -55,6 +55,13 @@ On Windows, the default output path is:
 build/bin/ocswitch-desktop.exe
 ```
 
+Note:
+
+- Windows 11 generally includes the WebView2 Runtime, and most mainstream Windows 10 devices already have it installed.
+- `ocswitch-desktop.exe` is distributed as a single-file artifact and does not require extra sidecar files in the same directory.
+- If the desktop app fails to start on Windows, one common cause is a missing WebView2 Runtime. Install the Microsoft Edge WebView2 Runtime and try again:
+  https://developer.microsoft.com/microsoft-edge/webview2/
+
 ### Development mode
 
 To run the desktop GUI in local development mode: