Next Build --Webpack Drops Semicolon After CSS @Layer Statement

The semicolon after the @layer statement is stripped by cssnano's postcss-normalize-whitespace plugin during CSS minification in the webpack build. This plugin incorrectly treats the semicolon as redundant whitespace, failing to preserve the CSS syntax requirement that a standalone @layer statement must end with a semicolon before a following block at-rule.

1. Clone https://github.com/Poliklot/next-css-layer-statement-semicolon-repro 2. Run `npm install` 3. Run `npm run build` (using `next build --webpack`) 4. Inspect the emitted CSS; observe that `@layer reset, tokens, base, components, utilities` lacks a semicolon before the next `@layer reset{...}` block, resulting in invalid CSS.

Disabling normalizeWhitespace may slightly increase CSS file size due to retained whitespace and newlines. Future updates to Next.js or css-minimizer-webpack-plugin may change the constructor name or options structure, causing this override to silently fail and the bug to reappear. Rollback: remove the webpack override or set normalizeWhitespace back to true. This workaround only applies to webpack builds; if switching to Turbopack, this configuration is ignored, but Turbopack may not exhibit the issue. Also, if other PostCSS plugins rely on normalized whitespace, this change could lead to unexpected output.