feat(desktop): add Electron desktop pet for Claude CLI

- Electron + React + TypeScript 桌面宠物外壳
- xterm.js + node-pty 直接对接 Claude CLI 进程
- 宠物 orb（80x80）可拖拽，点击展开终端面板
- CRT 复古终端主题（扫描线、文字发光）
- 全局快捷键 Cmd+Shift+C 显隐
- 窗口位置自动保存
- 中华田园犬吉祥物 icon（AI 生成）
- Makefile 新增 `make app` 打包命令

desktop/electron/preload.js

@@ -0,0 +1,24 @@
+const { contextBridge, ipcRenderer } = require('electron')
+
+const api = {
+  pty: {
+    write: (data) => ipcRenderer.send('pty:write', data),
+    resize: (cols, rows) => ipcRenderer.send('pty:resize', cols, rows),
+    onData: (callback) => {
+      ipcRenderer.on('pty:data', (_event, data) => callback(data))
+    },
+    onExit: (callback) => {
+      ipcRenderer.on('pty:exit', (_event, code) => callback(code))
+    },
+  },
+  window: {
+    expand: () => ipcRenderer.send('window:expand'),
+    collapse: () => ipcRenderer.send('window:collapse'),
+    setPosition: (x, y) => ipcRenderer.send('window:set-position', x, y),
+    setIgnoreMouseEvents: (ignore) => ipcRenderer.send('window:set-ignore-mouse', ignore),
+    close: () => ipcRenderer.send('window:close'),
+    minimize: () => ipcRenderer.send('window:minimize'),
+  },
+}
+
+contextBridge.exposeInMainWorld('petAPI', api)