This PR implements the requested repository cleanup by removing all content from the main branch, leaving only an empty repository structure.

Changes Made

• Removed all 73 files from the repository including:
  • Documentation (docs/ directory with README.md, index.html, errata.md, and images)
  • Educational content (Homework/ directory containing 15+ assignments with notebooks, PDFs, and associated files)
  • Configuration files (.gitignore, .github/ directory with issue templates)
  • Assets (assets/ directory with images and media files)
  • Legal documentation (LICENSE file)
  • System files (.DS_Store files)

Result

The repository now contains 0 files outside of the .git directory, effectively creating a clean slate while preserving the git history. This addresses the requirement to "清空 LeeZ-xtt/leedl-tutorial 仓库主分支（main）所有内容，不保留任何文件（包括 README、LICENSE 等），仅留下一个空仓库" (Clear all content from the main branch of the LeeZ-xtt/leedl-tutorial repository, keeping no files including README, LICENSE etc., leaving only an empty repository).

When merged, this will result in a completely empty repository as requested, ready for new content to be added in the future.

This pull request was created as a result of the following prompt from Copilot chat.

清空 LeeZ-xtt/leedl-tutorial 仓库主分支（main）所有内容，不保留任何文件（包括 README、LICENSE 等），仅留下一个空仓库。

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