Polish Rspress V2 introduction docs (EN/ZH)

[Copilot]

Rspress V2 intro docs needed clearer, up-to-date guidance for both English and Chinese readers.

• English intro refresh – Sharpened positioning, performance story (Rust toolchain), and capability bullets; clarified nav/sidebar configuration guidance.
• Chinese intro refresh – Smoothed sentence flow, tightened performance narrative, and separated declarative vs. programmatic nav/sidebar guidance for readability.
• Consistency – Kept structure intact while aligning MDX, SSG, search, theming, and plugin descriptions across languages.

Example excerpt (EN):

Rspress is a static site generator based on Rsbuild and rendered with React. It ships with a ready-to-use documentation theme so you can launch a site quickly, and it remains easy to tailor for blogs, product pages, or component libraries through theme overrides and official plugins.

Original prompt

从用户使用角度，在 website 中润色 Rspress V2 的 .mdx 文档

要求：

1. 同时润色中英文
2. 可调整排版，文章结构等，用更合适的表达，只要符合用户使用
3. 如果遇到过时内容或者与实际使用不一致的可以进行更新

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[github-actions]

Rsdoctor Bundle Diff Analysis

📁 web

Path: website/doc_build/web/rsdoctor-data.json

📌 Baseline Commit: b4258eba02 | PR: #2874

Metric	Current	Baseline	Change
📊 Total Size	14.6 MB	14.6 MB	0 B (0.0%)
📄 JavaScript	13.9 MB	13.9 MB	0 B (0.0%)
🎨 CSS	114.0 KB	114.0 KB	0 B (0.0%)
🌐 HTML	0 B	0 B	N/A
📁 Other Assets	502.5 KB	502.5 KB	0 B (0.0%)

📦 Download Diff Report: web Bundle Diff

Generated by Rsdoctor GitHub Action