test: add WXT test engineering

[jevin98]

Summary

• Add a Vitest test setup for the WXT/Vue extension, including WXT browser mocks, Vue SFC support, happy-dom, and coverage configuration.
• Add unit tests for CSS diff helpers, style formatting, array header formatting, and the DevTools panel shell.
• Add a Playwright smoke test that builds the Chrome extension, serves the build output locally, and verifies the built DevTools panel renders with mocked extension APIs.
• Extract CSS diff/filter logic into a pure utility and harden style formatting/message sending edge cases.
• Merge the latest main changes into this branch, preserving Tailwind v4 and _locales browser i18n updates.

Validation

• pnpm test
• pnpm compile
• pnpm test:e2e
• pnpm exec eslint .

Notes

• gh CLI is not installed in this environment, so PR creation used the GitHub plugin connector after pushing the branch with local git.

[jevin98]

@codex review

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit:92b62328b3

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[chatgpt-codex-connector]

Keep localized READMEs in sync

The new Testing section is added only to README.md, while README.zh-CN.md still jumps from build/zip instructions directly to the tech stack. This violates the repository instruction in AGENTS.md that generated README changes must be present and synchronized across all language variants, so Chinese readers will not see the newly documented test commands or E2E behavior. I checked the only other README with find . -maxdepth 3 -iname '*readme*' -print.

Useful? React with 👍 / 👎.

[jevin98]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Delightful!

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".