Refactor bilingual README for clarity and replace Mermaid diagrams with Excalidraw-based PNG images

[Copilot]

This updates the Chinese and English READMEs to be clearer, shorter, and structurally consistent. Based on feedback, Mermaid diagrams were removed and replaced with PNG images exported from Excalidraw sources, preserving the same architecture, command-set, and interaction content.

• Documentation flow rewrite (CN/EN aligned)

  • Reorganized both README.md and README(zh-cn).md into the same section sequence and intent.
  • Tightened wording in overview, protocol, command sets, and usage to reduce redundancy and improve scanability.

• Mermaid-to-image migration (feedback update)

  • Removed Mermaid blocks from both READMEs.
  • Switched to static PNG diagrams for:
    • framework architecture
    • command sets
    • client interaction flow
  • Added corresponding editable Excalidraw source files under .doc/*.excalidraw.
  • Renamed diagram assets to descriptive filenames and updated README references accordingly.

• Terminology, consistency, and accessibility

  • Kept CN/EN structure and semantics aligned.
  • Normalized diagram naming conventions across both READMEs.
  • Improved image alt text descriptions in both languages.

Example diagram used in README:

[nevstop]

对mermaid 图不满意，不要再使用这些已经生成的图，我希望生成和原图一样的 excalidraw 版本的图片，然后导出为 png 替换当前的图片

[Copilot]

Pull request overview

This PR refactors the project’s bilingual documentation to be shorter and structurally aligned between English and Chinese, while replacing previously embedded static diagrams/screenshots with equivalent Mermaid diagrams.

Changes:

• Rewrote/reshaped sections in README.md and README(zh-cn).md to follow the same flow and reduce redundancy.
• Replaced static image embeds with three Mermaid diagrams (architecture, command taxonomy, and client/server interaction) in both READMEs.
• Normalized terminology and command/protocol naming across CN/EN.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
README.md	English README rewrite + Mermaid diagrams for architecture/commands/sequence flow.
README(zh-cn).md	Chinese README rewrite mirroring the English structure + same Mermaid diagrams localized.

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[Copilot]

对mermaid 图不满意，不要再使用这些已经生成的图，我希望生成和原图一样的 excalidraw 版本的图片，然后导出为 png 替换当前的图片

已按要求移除 Mermaid，并改为 PNG 图片；同时补充了对应的 Excalidraw 源文件（.doc/*.excalidraw），README 中已切换到新的图片资源。对应提交：1403a85。

截图：