docs: publish bilingual project guides

[KXHXK]

Summary

• replace the mixed-language README with a project-focused English default page and a separate Simplified Chinese page
• expand both contribution guides with development, Agent safety, quality, and PR rules
• remove resume-oriented and obsolete multi-project entry points from the public README
• add document-index and anti-drift test coverage

Verification

• 14 release/document-index tests passed
• Ruff and formatting checks passed for the changed test
• repository safety checks passed
• bilingual heading parity, local links, and project-focus rules passed

Boundary

• no runtime behavior, API contract, database schema, or deployment state changed