docs(landing): interactive pillars, section bands, and copy polish

Replace the duplicate BYOK block with hover/tap detail panels under
the differentiators, drop the hero title period, center the matrix
footnote, and alternate section washes so vs / steps read as separate bands.

CHANGELOG.md

@@ -14,7 +14,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - **DEBUG demo seed URL**: `osgkeyboard://seed-demo` fills Home stats, History, and Dictionary with placeholder data and turns iCloud sync off (script: `scripts/seed_demo_data.py`). / **DEBUG 演示数据**：`osgkeyboard://seed-demo` 填充首页统计、历史与词库占位数据并关闭 iCloud 同步（脚本：`scripts/seed_demo_data.py`）。
 
 ### Changed
-- **Landing section copy**: richer pillars / BYOK / setup steps; titles →「开源，尽是不同」「BYOK，不花冤枉钱」「开箱可用，只要三步」。 / **落地页文案**：丰富差异柱、BYOK 与上手三步；标题改为「开源，尽是不同」「BYOK，不花冤枉钱」「开箱可用，只要三步」。
+- **Landing section copy**: richer interactive pillars (hover/tap detail stage; BYOK panel absorbs former BYOK block) plus competitor matrix; titles →「开源，尽是不同」/ setup「开箱可用，只要三步」。 / **落地页文案**：差异柱改为悬停/点按展开详情（BYOK 面板吸收原独立 BYOK 区）并加竞品对照表；标题含「开源，尽是不同」与「开箱可用，只要三步」。
 - **Unified welcome slogan**: iPad Home now reuses the iOS onboarding brand line, and macOS onboarding shows the same “Speak it. It’s typed.” welcome slogan. / **统一欢迎口号**：iPad 首页复用 iOS 引导页品牌句，macOS 引导页也显示同一句「开口即文字。」欢迎口号。
 - **GitHub Pages landing**: redesign as a commercial product page with zh/en, light/dark, brand mark, scroll motion, and App Store screenshots; emphasizes free, cross-platform, open source, privacy, and BYOK. / **GitHub Pages 落地页**：改版为商业产品页，支持中英与日夜模式、品牌标、滚动动效与 App Store 截图；突出免费、跨端、开源、隐私与 BYOK。
 - **Landing hero device family**: Mac + iPad + iPhone nested in one mockup cluster (no outer card stroke); screens swap with language/theme. / **落地页 Hero 设备组**：Mac、iPad、iPhone 叠放在同一组设备框内（无外卡片描边）；截图随语言/主题切换。