Add worker-based Typst source export

[Copilot]

Adds a Typst source export flow that packages template sources, generated .typ files, assets, and config into a downloadable zip, with the heavy compile/zip work executed inside the Typst worker.

Changes Made

• Build the Typst export archive in the compiler worker for better isolation and performance.
• Preserve the “导出为 typst 源码” menu entry and update it to call the worker-backed exporter.
• Harden asset mapping, file extension resolution, and missing-image error messages for export.
• Keep a dedicated export helper module that delegates to the worker.

Testing

• ✅ npm run lint
• ✅ npm run test
• ✅ npm run build

UI

Screenshot: https://github.com/user-attachments/assets/da202edf-55e0-40c6-b6ea-67f44943a24e

Original prompt

---

This section details on the original issue you should resolve

<issue_title>导出为 typst 源码</issue_title>
<issue_description>有时候可能需要对 pdf 进行深度修改，比如将 测试点数目 改称 子任务数目。导出为 typst 源码可以方便进行客制化修改

虽然关掉 NOI 模式可以改成子任务数目，但有可能我即想要文件夹子目录又想要绑包</issue_description>

<agent_instructions>实现导出为 typst 源码功能。
功能入口位于菜单栏的“文件”下，添加一个“导出为 typst 源码”的菜单项。
点击按钮后，将整个项目导出为一个压缩包，里面包含了 typst 源码，config.json 以及相关静态文件。导出后的压缩包应当可以直接编译。</agent_instructions>

Comments on the Issue (you are @copilot in this section)

@Mr-Python-in-China

可以做，不过导出出来的东西基本完全不可读，我只考虑了编译器能识别</comment_new>

• Fixes 导出为 typst 源码 #90

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View logs

[Mr-Python-in-China]

@copilot 把exportTypstArchive相关逻辑移动到一个新文件中以方便管理

[Copilot]

@copilot 把exportTypstArchive相关逻辑移动到一个新文件中以方便管理

已将 exportTypstArchive 相关逻辑移动到 src/utils/exportTypstArchive.ts，并更新调用处。提交：7fdc524。截图： https://github.com/user-attachments/assets/4555d0c7-f4be-4a58-bb9e-c8c801fe74a6

[Mr-Python-in-China]

@copilot 把编译和打包成zip的逻辑做到 worker 中

[Copilot]

@copilot 把编译和打包成zip的逻辑做到 worker 中

已将编译与打包 zip 的逻辑迁移到 compiler worker，并在主线程通过 worker 生成压缩包。提交：e165dfc。截图：https://github.com/user-attachments/assets/da202edf-55e0-40c6-b6ea-67f44943a24e

[Mr-Python-in-China]

@copilot 提到一个单独的模块，然后在worker中动态导入以减少网络请求