feat(font): Google Fonts preconnect 추가 및 system-ui 폴백 TDD

lib/exporter/font.optimization.test.ts

@@ -0,0 +1,29 @@
+import { describe, it, expect } from 'vitest'
+import { exportPage } from '@/lib/exporter/html'
+import { pageSchema, type Page } from '@/lib/schema/page'
+
+function makePage(): Page {
+  return pageSchema.parse({
+    title: 'Font Opt',
+    locale: 'en',
+    theme: { primaryColor: '#2563eb', fontFamily: 'Inter' },
+    sections: [ { type: 'hero', props: { heading: 'Hello', subheading: 'World', imageUrl: 'https://img/h.png' } } ],
+    form: { actionUrl: '', fields: [], spamProtection: { honeypotFieldName: '_hp', minSubmitSeconds: 2 } },
+    seo: { title: 't', description: 'd' },
+  })
+}
+
+describe('폰트 최적화', () => {
+  it('head에 Google Fonts preconnect 링크가 포함된다', () => {
+    const page = makePage()
+    const out = exportPage(page)
+    expect(out.html).toContain('<link rel="preconnect" href="https://fonts.googleapis.com"')
+    expect(out.html).toContain('<link rel="preconnect" href="https://fonts.gstatic.com" crossorigin')
+  })
+
+  it('CSS에 system-ui 폴백이 포함된다', () => {
+    const page = makePage()
+    const out = exportPage(page)
+    expect(out.css).toMatch(/font-family:[^;]*system-ui/i)
+  })
+})

lib/exporter/html.ts

@@ -254,6 +254,7 @@ function buildHead(page: Page) {
     <meta charset="utf-8" />
     <meta name="viewport" content="width=device-width, initial-scale=1" />
     <link rel="canonical" href="/" />
+    <link rel="preconnect" href="https://fonts.googleapis.com" />
     <title>${escapeHtml(page.seo.title)}</title>
     <meta name="description" content="${escapeHtml(page.seo.description)}" />
     <meta property="og:title" content="${escapeHtml(page.seo.title)}" />