Fix ins/mark markdown rendering without crashing previews

[tiankaima]

Motivation

• The previous approach using remark-ins/remark-mark caused the comment preview rendering to break in this environment, so a safer in-tree transformation was required to restore previews.
• Keep comment previews resilient while still supporting ++insert++ and ==mark== inline syntaxes.

Description

• Removed the incompatible remark-ins and remark-mark packages and updated the lockfile and package.json to reflect their removal.
• Added an in-repo rehype transform rehypeInsMark in src/components/comments/comment-markdown.tsx that turns ++...++ into <ins> and ==...== into <mark> at the HAST stage.
• Registered rehypeInsMark in the rehypePlugins list used by ReactMarkdown and ensured ins/mark are allowed in the custom sanitize schema.
• Kept and adjusted the existing markdown pipeline (including remarkGfm, remarkMath, remarkSupersub, remarkDirective, and remarkEmoji) and left the MarkdownErrorBoundary fallback to avoid full-page crashes.

Testing

• Ran bun remove remark-ins remark-mark, which completed successfully and updated the lockfile. (success)
• Started the dev server with bun dev (launching next dev) and requested GET /comments/guide, which returned 200 OK indicating the page served. (success)
• Executed a Playwright script that navigated to /comments/guide and produced the screenshot artifact artifacts/markdown-ins-mark-fixed.png, confirming the comment preview renders; unrelated TLS/font download warnings and an Auth MissingSecret error causing GET /api/auth/session 500 were observed but did not block the preview render. (warnings present, page render succeeded)

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Codex Task

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Project	Deployment	Actions	Updated (UTC)
server-nextjs	Ready	Preview, Comment	Jan 30, 2026 1:02pm