[codex] Add open-source README overview

[Pigbibi]

Summary

• Add a bilingual investment-risk notice near the top of the README.
• Add an open-source oriented overview explaining what the repository does, current status, quick start, safe deploy/operation path, and evidence/performance boundary.
• Keep the existing detailed runbooks and historical notes below the new entry section.

Validation

• README coverage script checked Chinese and English risk notices plus overview, quick start, deploy/operate, and evidence sections.
• git diff --check

Notes

This PR is documentation-only and does not change runtime behavior, workflows, credentials, or strategy defaults.

[chatgpt-codex-connector]

💡 Codex Review

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Reviewed commit: 832fd4bd7b

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[chatgpt-codex-connector]

Use a quick-start install command this repo supports

In a fresh checkout this command cannot work because the repository does not include packaging metadata (pyproject.toml, setup.cfg, or setup.py; I checked the tracked files with rg --files), so pip install -e '.[test]' fails before users can run the advertised test command. For the new open-source entry point, this blocks the documented onboarding path; point users at the existing requirements.txt/venv flow or add the missing package metadata and test extra.

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