[mosugi]

Summary

• Render ```mermaid fenced code blocks in comment bodies as diagrams, matching GitHub's behavior in review comments
• Mermaid was previously rendered only in the Markdown file preview (Support for Mermaid preview through GitHub Flavored Markdown support #246, Add Mermaid support for markdown diffs #247); comments showed the raw source as a highlighted code block

Implementation notes

• src/client/components/CommentBodyRenderer.tsx: the pre renderer passes mermaid-language blocks to the existing MermaidDiagram component, wrapped in my-2 to match the spacing of other comment blocks
• Reusing MermaidDiagram keeps the behavior identical to the file preview: mermaid is lazy-loaded, securityLevel: 'strict', the diagram follows the light/dark theme, and it falls back to the raw source when parsing fails
• Empty mermaid blocks fall through to the existing empty-code-block path, same as in MarkdownDiffViewer

Screenshots

Test plan

• Added tests in CommentBodyRenderer.test.tsx: a mermaid block renders as a diagram, and a parse error falls back to the source (mermaid is mocked as in MarkdownDiffViewer.test.tsx)
• pnpm test — full Vitest suite passes (862 passed / 2 skipped)
• pnpm check — oxlint type-aware checks pass
• pnpm build — production build succeeds
• Manually verified with --comment containing a mermaid block; the diagram renders inside the comment thread

[mosugi]

commentでもmermaidが表示できると嬉しいので、マージしてもらえると嬉しいです。レビューよろしくお願いします🙏