Sync Chinese quick-start documentation with English version

[Copilot]

The Chinese quick-start.md contained outdated concepts (text-schema, JSON schema, NarrativeTextVis) that diverged from the English version's focus on T8's declarative syntax.

Changes

• Info-box section: Replaced text-schema/JSON explanation with declarative syntax messaging

  • Reframed from "why not use text-schema" to "why use T8's declarative syntax"
  • Updated advantages list to emphasize LLM-friendliness, declarative nature, and framework agnosticism
  • Applied proper Chinese punctuation (full-width dashes)

• Features section: Updated terminology from text-schema to T8 语法

  • Changed "解析文本结构描述 json schema 为 html" to "将 T8 语法结构解析为语义化的 HTML 元素"
  • Clarified rendering engine description to match English version

Before vs After

Before:

**_`text-schema` 构建成本高不如直接拼接 DOM 快，我为什么还要用 T8？_**

要解答这个问题需要先明确 `JSON` 从哪儿来？
narrative 相关技术基于 `JSON` 数据来自 LLM 大模型生成的假设...

After:

**_"为什么我应该使用 T8 而不是直接拼接 DOM？"_**

答案在于 T8 的**声明式语法** —— 这是其与众不同的核心特性。
T8 语法是一种轻量级的、基于 Markdown 的 DSL（领域特定语言）...

All other Chinese-English documentation pairs in site/ verified to be structurally consistent.

Original prompt

https://github.com/antvis/T8/blob/main/site/zh/tutorial/quick-start.md 的内容和 英文内容不匹配，按照英文内容重新组织一下。并检查一下 site 目录的其他中英文是否一致的。

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