[BF-001] Replace the root language selector with a full x-default landing page

[baixiangcpp]

Issue

Closes #19

Scope

• Complete the reopened BF-001 root / x-default landing page requirements.
• Keep / crawlable and useful without a forced locale redirect.
• Add full root landing copy to every supported locale so new copy is not English-only.
• Strengthen the root page guard for the reopened acceptance criteria.

Implementation

• Reworked src/app/page.tsx so / now has a full H1, value proposition, search entry, Browse all tools, Install app, free/no-account/local-first proof points, 8 popular tools, 8 category links, Privacy Policy, Trust Center, and language links.
• Kept canonical and x-default hreflang on root via existing SEO helpers.
• Removed no locales and added complete site.root_* copy for en, zh-CN, zh-TW, ja, ko, de, and fr.
• Updated tests/guards/root-page-redirect-guard.test.tsx to enforce no redirect script, complete root content, all locale alternates, indexable robots, and all-locale root copy coverage.

Acceptance Criteria

• Visiting / shows a full homepage, not a language-only interstitial.
• Root page includes clear H1, value proposition, search entry point, popular tools, category links, privacy/trust copy, and language switcher.
• Root page is useful before hydration through normal links to search/all tools/install/language pages.
• There is no forced first-visit redirect from / to a locale page.
• All existing locale homepages remain available.
• / has canonical set to https://byteflow.tools/.
• / has hreflang=\"x-default\" pointing to https://byteflow.tools/.
• / has hreflang alternates for en, zh-CN, zh-TW, ja, ko, de, and fr.
• All localized homepages retain reciprocal hreflang alternates.
• / and all localized homepages are in sitemap.
• Root metadata is distinct and descriptive.
• Root page is indexable.
• Language switcher, search entry point, and popular tool links are keyboard-accessible links.
• Focus states are visible through existing focus-visible ring classes.
• Mobile layout is usable; screenshot captured.
• No blocking modal appears on first visit.
• All new root copy is present in every supported locale.

Validation

• npm run lint - PASS
• npm run test - PASS, 224 files / 1125 tests
• npm run validate - PASS, including i18n, i18n QA, privacy copy, analytics taxonomy, security, bundle, SEO, and type gates
• npm run build - PASS, generated 1401 static pages; canonical/hreflang, metadata localization, JSON-LD, rendered i18n copy, localized content, and service worker post-build gates passed
• npm run test:e2e:smoke - PASS
• npm run check:canonical - PASS, 1394 pages verified
• npm run check:hreflang - PASS, 1394 pages verified
• npm run check:sitemap-lastmod - PASS
• npm run check:i18n - PASS; same-as-en effective count remains 0 for all non-en locales

Manual Checks

• Desktop screenshot captured: output/playwright/bf-001-root-desktop.png.
• Mobile screenshot captured: output/playwright/bf-001-root-mobile.png.
• Root evidence captured: output/playwright/bf-001-root-evidence.json.
• Evidence: canonical=https://byteflow.tools, alternateCount=8, x-default=https://byteflow.tools, h1=123 Local Browser Tools for Developers.
• Evidence: no forced redirect on desktop/mobile local static root URL.
• Evidence: root includes search, install, Trust Center, and language chooser; thin prompt is absent.

Privacy Check

• 不采集工具输入
• 不采集工具输出
• 不新增未披露的外部请求
• 不持久化敏感 payload
• No cookies, geolocation routing, user-level tracking, analytics payloads, or third-party scripts were added.

Screenshots / Evidence

• Desktop: output/playwright/bf-001-root-desktop.png
• Mobile: output/playwright/bf-001-root-mobile.png
• Metadata evidence JSON: output/playwright/bf-001-root-evidence.json

[cloudflare-workers-and-pages]

Deploying byteflow with    Cloudflare Pages

Latest commit:	c612500
Status:	✅  Deploy successful!
Preview URL:	https://44f95b17.byteflow-c58.pages.dev
Branch Preview URL:	https://fix-bf-001-root-x-default-co.byteflow-c58.pages.dev

View logs