refactor: 迁移至 electron-vite 官方推荐目录结构

- electron/* -> src/main/* (主进程)
- electron/preload.ts -> src/preload/index.ts (预加载)
- src/electron-api.d.ts -> src/preload/index.d.ts (类型声明)
- src/* -> src/renderer/src/* (渲染进程)
- src/index.html -> src/renderer/index.html
- electron.vite.config.ts 简化为自动入口检测 (零配置)
- tsconfig.app.json -> tsconfig.web.json, 更新 includes/paths
- 构建产物 dist-electron/ -> out/ (修复 main/preload 输出覆盖 bug)
- 更新 package.json main 字段 + electron-builder files
- 更新 .gitignore + eslint ignores
- 更新 AGENTS.md 架构文档

eslint.config.js

@@ -13,7 +13,7 @@ const commonLanguageOptions = {
 }
 
 export default tseslint.config(
-  { ignores: ['dist', 'dist-electron', 'release', 'coverage', 'node_modules'] },
+  { ignores: ['dist', 'out', 'release', 'coverage', 'node_modules'] },
   {
     extends: [js.configs.recommended, ...tseslint.configs.recommended],
     files: ['**/*.ts'],