feat(site): launch TraceGate Studio marketing experience

[Chloiris]

Summary

• add a commercial-grade bilingual TraceGate Studio product site in apps/site
• add independently designed light and dark themes; first visits always start in light and explicit choices persist under tracegate-site-theme
• preserve the original dark experience while moving page, surface, text, border, shadow, gradient, graph, status, overlay, and browser-chrome colors into semantic tokens
• add an accessible header theme control with Chinese/English labels, keyboard semantics, reduced motion, live theme-color, native color-scheme, and no navigation or state reset
• prevent theme flash with a small same-origin theme-init.js that runs before the React entry and CSS without adding script-src 'unsafe-inline'
• adapt the hero Evidence Graph, all workflow/architecture/security sections, responsive gallery, Lightbox, mobile drawer, screenshots, and Open Graph art to the new default theme
• retain the 15 explicitly scoped real-local / Playwright-fixture / controlled-benchmark product views and generated project facts
• keep deployment limited to /var/www/tracegate; no Studio application, Agent, database, benchmark, or production API behavior changed

Evidence boundaries

• fixture screenshots remain visibly labelled and are not presented as public-PR or live-model evidence
• real DeepSeek Autofix remains scoped to a synthetic temporary Git repository
• Windows packaging remains VERIFIED_WINDOWS_CI, not Windows GUI manual acceptance
• public-PR Autofix E2E remains BLOCKED
• no accuracy, customer, user-count, or automatic-fix success claims were added

Validation

• pnpm site:lint — passed with zero warnings
• pnpm site:typecheck — passed
• pnpm site:test — 16 tests passed
• TRACEGATE_SITE_CAPTURE=1 pnpm site:test:e2e — 10 tests passed across light/dark, persistence, Chinese/English, 375/390/430/768/1024/1440/1920 widths, drawer, Lightbox, Autofix, resources, and reduced motion
• pnpm site:build — passed
• pnpm site:lighthouse — Performance 100, Accessibility 100, Best Practices 100, SEO 100
• final build: 101 files, about 2.6 MB; CSS 56.83 kB / 11.77 kB gzip; entry JS 216.52 kB / 70.70 kB gzip
• secret/file audit and git diff --check — passed

Deployment status

The 101-file static build was uploaded through the restricted SSH alias to /var/www/tracegate. Local and remote SHA-256 values match for index.html, theme-init.js, and og-tracegate.png; the origin Nginx Host check returns HTTP 200.

Public acceptance is blocked, not passed: the cloud provider currently intercepts the unfiled domain with HTTP 403, and HTTPS is unavailable because Certbot has not produced a certificate. The prior ACME attempt also recorded a transient CAA SERVFAIL. Complete ICP filing and successful HTTP/HTTPS public checks remain external gates. No other /var/www directory or virtual host was modified.

Theme screenshots

• docs/site-screenshots/light-desktop-1440-home.png
• docs/site-screenshots/dark-desktop-1440-home.png
• docs/site-screenshots/light-desktop-autofix.png
• docs/site-screenshots/dark-desktop-autofix.png
• docs/site-screenshots/light-mobile-390-home.png
• docs/site-screenshots/dark-mobile-390-home.png
• docs/site-screenshots/light-mobile-navigation.png
• docs/site-screenshots/dark-mobile-navigation.png