docs: split bilingual open-source readmes

[Pigbibi]

Summary

• replace the mixed-language README with an English-only open-source entry point
• add a separate Chinese README.zh-CN.md with the same project overview structure
• include explicit risk notices, quick start, deployment guidance, and evidence boundaries

Validation

• verified README.md contains no Chinese characters
• verified README.zh-CN.md exists and contains the Chinese risk notice
• verified only README.md and README.zh-CN.md changed

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Install the test extra in quick start

For a fresh clone, python -m pip install -e . does not install the optional test dependency declared in pyproject.toml (test = ["pytest>=8"]), so the next documented command python -m pytest -q can fail with No module named pytest in a clean environment. The previous README used python -m pip install -e '.[test]'; please keep that here and in the matching Chinese quick-start command.

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