Generate one Cankun blog preview

Treat one article slug, including its English and Chinese MDX pair, as the complete transaction. Never turn a single-article request into an archive-wide regeneration.

Preflight

1. Confirm the workspace is cankun-blog and contains:
   • content/files/
   • content/preview-image-prompts.md
   • public/images/
   • scripts/optimize-previews.ts
2. Resolve exactly one target slug. If the user did not name it, select it only when exactly one English MDX article lacks preview metadata; otherwise ask which article.
3. Inspect git status and preserve unrelated changes.
4. Check whether the target already has a preview PNG or WebP. Overwrite it only when the user explicitly asked to refresh, replace, remake, or restyle it; otherwise report the existing asset and stop.
5. Remember that bun run previews scans every public/images/**/*-preview.png. Check for unrelated stale sources before running it; stop and report a scope conflict if the command would regenerate another article's WebP.

Read the sources of truth

Read the target English article fully. Read its Chinese pair when present so the alternative text can be localized accurately.