fix(rsbuild): load StyleX styles via extracted stylex.css

[heyq02]

Summary

• Disable StyleX runtimeInjection and link the emitted stylex.css from public/index.html in rsbuild/stylex.
• Update the example README to document why the CSS link is required for production builds.

Fixes #356

Test plan

• pnpm --filter @rsbuild-example/stylex build succeeds
• dist/stylex.css is emitted and dist/index.html contains <link rel="stylesheet" href="/stylex.css" />
• pnpm --filter @rsbuild-example/stylex preview — StyleX styles render (stylex.css loads, h1 font-size: 3.6rem / font-weight: 700, flex column layout)
• pnpm --filter @rsbuild-example/stylex dev — same StyleX styles render via /stylex.css

[chenjiahan]

Thanks for the fix! Hardcoding /stylex.css bypasses Rsbuild’s CSS asset handling, including content-hashed filenames and inlineStyles.

Disabling runtime injection in dev also breaks style HMR: class names update, but the stylesheet only updates after a page refresh.

Could we try the official @stylexjs/unplugin instead? It may be a better fit.

[heyq02]

Thanks for the review — addressed in a621f95.

Changes

• Replaced unplugin-stylex with official @stylexjs/unplugin
• Removed hardcoded /stylex.css HTML link
• StyleX CSS now appends into Rsbuild’s content-hashed CSS asset (static/css/index.<hash>.css)

Note

Used stylex.webpack() instead of stylex.rspack(): the unplugin’s CSS injection currently attaches through the webpack-compatible hook; with stylex.rspack() only the transform ran and CSS was not emitted. Transform + injection both work via stylex.webpack() under tools.rspack.plugins.

Verified with pnpm build / pnpm preview.