docs: update lightningcss default notes (#21907)

Author: bluwy

docs/config/build-options.md

@@ -130,7 +130,7 @@ In this case, you need to set `build.cssTarget` to `chrome61` to prevent vite fr
 ## build.cssMinify
 
 - **Type:** `boolean | 'lightningcss' | 'esbuild'`
-- **Default:** the same as [`build.minify`](#build-minify) for client, `'lightningcss'` for SSR
+- **Default:** `'lightningcss'`, but `false` if [`build.minify`](#build-minify) is disabled for client build
 
 This option allows users to override CSS minification specifically instead of defaulting to `build.minify`, so you can configure minification for JS and CSS separately. Vite uses [Lightning CSS](https://lightningcss.dev/minification.html) by default to minify CSS. It can be configured using [`css.lightningcss`](./shared-options.md#css-lightningcss). Set the option to `'esbuild'` to use esbuild instead.
 

docs/guide/features.md

@@ -353,17 +353,11 @@ Default and named imports from CSS files (e.g `import style from './foo.css'`) a
 
 ### Lightning CSS
 
-Starting from Vite 4.4, there is experimental support for [Lightning CSS](https://lightningcss.dev/). You can opt into it by adding [`css.transformer: 'lightningcss'`](../config/shared-options.md#css-transformer) to your config file and install the optional [`lightningcss`](https://www.npmjs.com/package/lightningcss) dependency:
+Vite uses [Lightning CSS](https://lightningcss.dev/) to minify CSS in production builds by default. However, PostCSS is still used for other CSS processing.
 
-```bash
-npm add -D lightningcss
-```
-
-If enabled, CSS files will be processed by Lightning CSS instead of PostCSS. To configure it, you can pass Lightning CSS options to the [`css.lightningcss`](../config/shared-options.md#css-lightningcss) config option.
-
-To configure CSS Modules, you'll use [`css.lightningcss.cssModules`](https://lightningcss.dev/css-modules.html) instead of [`css.modules`](../config/shared-options.md#css-modules) (which configures the way PostCSS handles CSS modules).
+There is experimental support for using Lightning CSS for CSS processing entirely. You can opt into it by adding [`css.transformer: 'lightningcss'`](../config/shared-options.md#css-transformer).
 
-By default, Vite uses esbuild to minify CSS. Lightning CSS can also be used as the CSS minifier with [`build.cssMinify: 'lightningcss'`](../config/build-options.md#build-cssminify).
+To configure it, you can pass Lightning CSS options to the [`css.lightningcss`](../config/shared-options.md#css-lightningcss) config option. To configure CSS Modules, you should use [`css.lightningcss.cssModules`](https://lightningcss.dev/css-modules.html) instead of [`css.modules`](../config/shared-options.md#css-modules) (which configures the way PostCSS handles CSS modules).
 
 ## Static Assets