docs(site): switch hero to React Bits–style beams

Replace the wave gradient with a vanilla Three.js beams field using the
shared demo preset and OSG green lighting for a more dimensional look.

CHANGELOG.md

@@ -8,7 +8,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 
 ### Added
-- **Wave Gradient hero**: Stripe-style animated mesh gradient (vendored MIT `wave-gradient`) with OSG green/teal/violet palettes, reduced-motion freeze, and CSS fallback. / **Wave Gradient Hero**：Stripe 风格动态网格渐变（本地托管 MIT `wave-gradient`），配 OSG 绿/青/紫配色，支持减少动态模式冻结与 CSS 回退。
+- **Beams hero**: radiant noise-warped beam array (React Bits–style, vanilla Three.js) with the shared demo preset (26 beams, 208° rotation) and OSG green light. / **Beams Hero**：放射状噪声光束阵列（React Bits 风格，原生 Three.js），采用分享的演示预设（26 束、208° 旋转）与 OSG 绿色灯光。
 - **App Store download badges**: official badges on bilingual READMEs (hero + Get sections) and the website, with China-store `/cn/` links for Chinese and regionless App Store links for English. / **App Store 下载徽章**：中英文 README（顶部与获取区）与官网挂载官方徽章；中文链 `/cn/`，英文用无地区链接。
 - **Website SEO & AI discovery**: richer meta/JSON-LD/FAQ, `llms.txt`, expanded sitemap, English landing, plus install / compare / Mac-dictation content pages. / **官网 SEO 与 AI 发现**：强化 meta/JSON-LD/FAQ、`llms.txt`、sitemap，并新增英文落地页与安装 / 对比 / Mac 听写专题页。
 - **Context-aware polish safeguards**: polish can use a redacted cursor-neighborhood snapshot for natural continuation, validates protected terms and identifiers, retries once, and falls back to a conservative local cleanup when needed. / **上下文润色护栏**：润色可使用经截断脱敏的光标附近文字自然衔接，并校验受保护词与标识符；失败时重试一次，仍不合格则降级为本地保守清理。