docs: update install instructions for Sparkle auto-update and GitHub Releases

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: demo

CLAUDE.md

@@ -57,6 +57,13 @@ cp -R "$APP_SRC" ./VPNMenuBar.app
 ditto -c -k --keepParent ./VPNMenuBar.app ./VPNMenuBar-0.1.0.zip
 ```
 
+**Signing for Sparkle** (after creating the zip):
+```sh
+# sign_update is from Sparkle's tools (find it in DerivedData or download from Sparkle releases)
+/path/to/sign_update ./VPNMenuBar-X.Y.Z.zip
+# Copy the edSignature and length into appcast.xml's new <item>
+```
+
 **Launch the built app for manual smoke testing**:
 ```sh
 open ./VPNMenuBar.app       # first run will hit Gatekeeper — right-click → Open
@@ -160,6 +167,7 @@ The repo IS the distribution. Three artifacts work together:
    - `brew install openconnect` (skipped if already installed)
    - Writes `/etc/sudoers.d/vpnmenubar-<user>` with a `visudo -c -f` pre-check. Uses `/etc/sudoers.d/` (not the main `/etc/sudoers`) so uninstall is `sudo rm` of one file and a broken rule can never lock the user out of sudo
    - Handles Intel vs Apple Silicon path differences automatically
+4. **`appcast.xml`** — Sparkle appcast feed at repo root. Each release adds a new `<item>` with the version, EdDSA signature, file size, and GitHub Release download URL. Sparkle checks this file periodically to discover updates. Updated manually as part of the release workflow.
 
 Gatekeeper bypass is `xattr -dr com.apple.quarantine /Applications/VPNMenuBar.app` or right-click → Open. Document this in any user-facing instructions.
 

INSTALL.md

@@ -37,6 +37,17 @@ macOS 状态栏小工具，封装 `openconnect` 连接 Cisco AnyConnect 兼容
 > bash install-deps.sh
 > ```
 
+## 从 GitHub Releases 下载（最简单）
+
+不需要 git，直接从 Release 页面下载最新版：
+
+1. 打开 [最新 Release](https://github.com/CoderZCC/VPNMenuBar/releases/latest)，下载 `VPNMenuBar-x.y.z.zip`
+2. 解压后把 `VPNMenuBar.app` 拖到 `/Applications`
+3. 终端执行 `xattr -dr com.apple.quarantine /Applications/VPNMenuBar.app`（或者右键 → 打开 → 打开）
+4. 启动后走 Onboarding 向导
+
+之后有新版本时，app 会**自动提示更新**，点"安装更新"即可，不用再手动下载。也可以随时从状态栏菜单点 **Check for Updates…** 手动检查。
+
 ---
 
 ## 手动安装步骤

README.md

@@ -16,6 +16,7 @@ A macOS 13+ status-bar app that wraps OpenConnect for Cisco AnyConnect-compatibl
 - **Auto-reconnect on network change** — drops the VPN cleanly when WiFi disconnects, reconnects automatically when it comes back (only if you connected manually — failed connects don't loop-retry)
 - **Stale host-route cleanup** — scrubs leftover routes from the previous WiFi gateway before each connect, fixing the "Failed to connect after WiFi switch" symptom
 - **Status-bar agent** — `LSUIElement`, no Dock icon, no notification spam
+- **Auto-update** — checks GitHub Releases for new versions via [Sparkle](https://sparkle-project.org/). One-click update from the menu bar
 
 ## Install
 
@@ -43,6 +44,14 @@ xcodebuild -project VPNMenuBar.xcodeproj -scheme VPNMenuBar \
 # See CLAUDE.md "Build, run, ship" for the full distribution recipe.
 ```
 
+### Option C — download from GitHub Releases
+
+Download the latest `VPNMenuBar-x.y.z.zip` from the [Releases](https://github.com/CoderZCC/VPNMenuBar/releases/latest) page:
+
+1. Unzip → drag `VPNMenuBar.app` to `/Applications`
+2. `xattr -dr com.apple.quarantine /Applications/VPNMenuBar.app`
+3. Open the app — subsequent updates will be delivered automatically via the menu bar
+
 ## First launch
 
 Right-click the app in Finder → **Open** → **Open** in the Gatekeeper warning. After that, normal launches work and the login-item registration happens automatically.