Task 083: コード引用のシンタックスハイライト

Status: DONE

Motivation

Human directive: 「コードを引用するときは syntax highlight させたい」

Implementation

• Library: highlight.js v11.11.1 via CDN (same approach as KaTeX)
• Theme: github-dark (matches site's dark color scheme)
• Language detection: Extracts language tag from fenced code blocks ( `typescript )
• HTML output: <pre><code class="language-typescript">...</code></pre>
• Initialization: hljs.highlightAll() on DOMContentLoaded
• CSS fix: pre code.hljs { background: transparent } to prevent double-background

Changes

• templates.ts: markdownToHtml() now extracts language tags, layoutHtml() includes hljs CDN
• templates.test.ts: 3 new tests (language class extraction, no-language fallback, XSS safety)
• 969 TS tests passing