fix: 迁移弃用的 xterm 依赖至 @xterm/xterm（Closes #122） (#128)

* fix: 迁移弃用的 xterm 依赖至 @xterm/xterm（#122）

- dependencies 移除 xterm@^5.3.0（已弃用）与 @xterm/addon-fit（二者始终
  内联进 lib/client-terminal.js 懒加载 chunk，运行时零依赖）
- 二者移至 devDependencies（构建期仍需：tsdown 内联 + CSS 构建期解析 + 类型）
- 代码与构建注释改用官方新包名 @xterm/xterm@^5.5.0（addon-fit@0.10.0 的
  peer 约束锁 ^5.0.0，不用 6.x），CSS 路径同步为 @xterm/xterm/css/xterm.css
- 消除用户安装时的 deprecated 警告与 missing peer @xterm/xterm 警告

* chore: 顺带升级 @xterm/addon-fit 至 ^0.11.0

- 0.11.0（2025-12 发布）不再声明 peer 依赖，消除 peer 解析噪音
- 其运行时 API（_renderService.clear / options.overviewRuler 兜底）与
  @xterm/xterm@^5.5.0 兼容：overviewRuler 在 5.x 为 undefined 时回退 14，
  与 0.10.0 行为一致；typecheck/build/test（515）/ 挂载门禁均通过

package.json

@@ -129,13 +129,11 @@
     "@codemirror/state": "^6.7.1",
     "@codemirror/view": "^6.43.8",
     "@lezer/highlight": "^1.2.3",
-    "@xterm/addon-fit": "^0.10.0",
     "clsx": "^2.1.1",
     "node-pty": "^1.1.0",
     "rxjs": "^7.8.2",
     "schemastery": "^3.18.0",
-    "ws": "^8.18.0",
-    "xterm": "^5.3.0"
+    "ws": "^8.18.0"
   },
   "devDependencies": {
     "@cordisjs/plugin-loader": "^1.0.0-rc.5",
@@ -159,6 +157,8 @@
     "@types/react": "~18.3.1",
     "@types/react-dom": "~18.3.1",
     "@types/ws": "^8.5.10",
+    "@xterm/addon-fit": "^0.11.0",
+    "@xterm/xterm": "^5.5.0",
     "cordis": "^4.0.0-rc.7",
     "jsdom": "^29.1.1",
     "lightningcss": "^1.32.0",