[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]

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[chatgpt-codex-connector]

Replace the non-existent editable install extra

In this repo as checked out for this review, there is no pyproject.toml, setup.py, or setup.cfg anywhere under the project, so the new Quick start command fails before installing dependencies (python -m pip install -e '.[test]' reports that the directory does not appear to be a Python project). New contributors following the top-of-README path will be blocked from running tests; the existing CI and lower README sections instead install from requirements-lock.txt/requirements.txt.

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