Added CSS build check by Actions

[hsbt]

This is remaining work of redesign project. We should check to css build every PRs.

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[Copilot]

Pull request overview

This pull request adds automated CSS build verification to the CI pipeline as part of the redesign project. The changes ensure that the compiled CSS file stays in sync with the source files by checking it on every pull request.

• Added Node.js setup and CSS build check to the GitHub Actions CI workflow
• Removed package-lock.json from .gitignore to track npm dependencies
• Added package-lock.json with Tailwind CSS and typography plugin dependencies

Reviewed changes

Copilot reviewed 1 out of 3 changed files in this pull request and generated 1 comment.

File	Description
.github/workflows/ci.yml	Adds Node.js setup, npm dependency installation, and CSS build verification steps before Ruby setup
.gitignore	Removes package-lock.json from ignore list to track it in version control
package-lock.json	Adds complete dependency tree for Tailwind CSS v3.4.17 and @tailwindcss/typography v0.5.19

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[Copilot]

The error message could be improved for clarity. Currently it says "Error: compiled.css is out of date" but it would be more helpful to specify which file needs to be regenerated and how to do it locally. Consider making the message more actionable, for example: "The compiled CSS is out of date. Please run 'npm run build-css' locally and commit the updated stylesheets/compiled.css file."

Suggested change

	git diff --exit-code stylesheets/compiled.css || (echo "Error: compiled.css is out of date. Run 'npm run build-css' and commit the changes." && exit 1)
	git diff --exit-code stylesheets/compiled.css || (echo "Error: The compiled CSS is out of date. Please run 'npm run build-css' locally and commit the updated stylesheets/compiled.css file." && exit 1)

[hsbt]

I'm not sure why npm run build-css at GitHub Actions generate the following diff:

+.rounded{
+  border-radius: 0.25rem;
+}
+
 .rounded-2xl{
   border-radius: 1rem;
 }
@@ -4567,6 +4571,10 @@ body:is(.dark *){
   text-decoration-line: underline;
 }
...