docs: move Chinese README into doc/ directory

[AperturePlus]

Motivation

• Reduce clutter in the root README.md by moving the Chinese documentation into a dedicated documentation directory.
• Make the repository layout clearer by centralizing non-English docs under doc/.

Description

• Created a new doc/ directory and added doc/README.zh-CN.md containing the migrated Chinese README content.
• Removed the Chinese section from the root README.md and replaced it with a pointer to doc/README.zh-CN.md.
• Kept the English acknowledgements in the root README.md.
• Changes were staged and committed with the message docs: move Chinese README content to doc directory.

Testing

• Verified the new file exists with test -f doc/README.zh-CN.md && echo ok, which returned ok.
• Inspected the working tree and diffs with git status --short and git diff to confirm only the intended files changed.
• Successfully committed the changes (git commit) confirming the update was recorded.

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Codex Task