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

tsconfig.web.json

@@ -0,0 +1,29 @@
+{
+  "compilerOptions": {
+    "tsBuildInfoFile": "./node_modules/.tmp/tsconfig.web.tsbuildinfo",
+    "target": "es2023",
+    "lib": ["ESNext", "DOM"],
+    "module": "ESNext",
+    "types": ["vite/client"],
+    "skipLibCheck": true,
+
+    /* Bundler mode */
+    "moduleResolution": "bundler",
+    "allowImportingTsExtensions": true,
+    "verbatimModuleSyntax": true,
+    "moduleDetection": "force",
+    "noEmit": true,
+
+    /* Path alias */
+    "baseUrl": ".",
+    "paths": {
+      "@renderer/*": ["src/renderer/src/*"]
+    },
+
+    /* Linting */
+    "noUnusedLocals": true,
+    "noUnusedParameters": true,
+    "noFallthroughCasesInSwitch": true
+  },
+  "include": ["src/renderer/src/**/*", "src/preload/**/*.d.ts"]
+}