docs: add Simplified Chinese translation (README.zh-CN.md)

[ltianyi992]

Summary

Adds a complete Simplified Chinese (简体中文) translation of the main README, addressing the i18n support request in #66.

The Chinese developer community is one of the largest open-source contributor communities worldwide; a native-language README significantly lowers the barrier to entry for engineers who find English documentation difficult.

What's included

• README.zh-CN.md — full translation of the main README.md:
  • All prose sections translated (intro, design patterns, factor list, disclaimers, related resources)
  • Section headings and blockquotes translated
  • All code blocks, image links, and GitHub URLs left unchanged so they remain functional
  • Visual navigation table preserved with translated alt-text
• README.md — a single line added under the opening paragraph:

  **Translations:** [简体中文](./README.zh-CN.md)
  

Translation approach

• Idiomatic Chinese rather than literal word-for-word translation
• Technical terms (DAG, LLM, context window, tool calls, etc.) kept as-is or with standard Chinese equivalents where established ones exist
• The author's informal, first-person voice preserved throughout

Closes #66

[CLAassistant]

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