[i18n] Add Chinese translation(zh) for smolagents

[Ayuilos]

This PR started from #141

• The following chapters translations are finished.

- title: Get started
  sections:
  - local: index
    title: 🤗 Agents
  - local: guided_tour
    title: Guided tour
- title: Tutorials
  sections:
  - local: tutorials/building_good_agents
    title: ✨ Building good agents
  - local: tutorials/tools
    title: 🛠️ Tools - in-depth guide
  - local: tutorials/secure_code_execution
    title: 🛡️ Secure your code execution with E2B
- title: Conceptual guides
  sections:
  - local: conceptual_guides/intro_agents
    title: 🤖 An introduction to agentic systems
  - local: conceptual_guides/react
    title: 🤔 How do Multi-step agents work?

• The video in 本地部署视频教程 #80 has been added to guided_tour.md
• For reason why this work has been finished so fast: I used Roo Cline extension on VSCode, and leverage DeepSeek V3 translate the docs for me, then my work is to check and adjust the translation details line by line. Big surprise is >90% worked so well which exceeded my personal expectations. I'm feeling like a safty officer in an auto-driving car, just to make sure it didn't do big wrong thing.

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👉 Here is discussion that need to be agreed upon. @FanwangM

I've chosed to not translate agent to 智能体 in docs because I think in this way it can be more "原汁原味", and reader could notice the "agent" easily in docs with almost Chinese charactors.

If you agree, I hope you could continue to follow this consensus in your translations.🙏