Add query parameter for panel widths

[landeqiming666]

Fixes #63.

This adds a small widths query parameter for embedded CodePan pages. It works with the existing show query parameter, so an embed can choose visible panes and their relative widths without changing the editor UI:

<iframe src="https://codepan.net/?readonly&show=js,console,output&widths=25,25,50"></iframe>

The implementation keeps the old equal-width behavior when widths is omitted, invalid, or does not match the visible pane count. I kept this intentionally narrower than the older PRs for this issue: no dependency updates, no layout rewrite, and no generated build output.

Verification:

• npm run test:pan-widths
• git diff --check
• npx -y -p node@18 -c 'NODE_OPTIONS=--openssl-legacy-provider npm run build'

Notes:

• npm test currently reaches the repository's existing XO baseline failures on this checkout (import order / import extension rules in files that this PR mostly does not touch). On Node 25 it also fails earlier because the old ESLint stack depends on APIs removed from modern Node. The focused width parser test and production build both pass as listed above.

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IssueHunt Summary

Referenced issues

This pull request has been submitted to:

• #63: add query string parameters for setting panel width

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[vercel]

@landeqiming666 is attempting to deploy a commit to the EGOIST's projects Team on Vercel.

A member of the Team first needs to authorize it.

[landeqiming666]

Hi maintainers, gentle follow-up on this PR.

The PR remains mergeable. The only red status I can see is the Vercel preview requiring authorization from the EGOIST team; Socket checks are green, and the local validation listed in the PR description passed before submission.

Could a maintainer review this when you have a chance, or authorize/re-run the Vercel preview if you want that check before review? I am happy to adjust the implementation if you prefer a different query parameter shape. Thanks!