fix(css): keep the descendant combinator before a pseudo-class when minifying

[breken-ai]

The CSS minifier removes whitespace on both sides of :. In a declaration that is fine, but in a selector the whitespace before a pseudo-class is the descendant combinator. Removing it changes which element the rule matches:

const cls = css`
  & :first-child {
    margin: 0;
  }
  .a :is(h1, h2) {
    color: red;
  }
`
// before: &:first-child{margin:0}.a:is(h1,h2){color:red}   (matches the element itself)
// after:  & :first-child{margin:0}.a :is(h1,h2){color:red}  (matches its descendants)

With this change the minifier removes only the whitespace after :. A single space before : is kept, and longer runs still collapse to one space as before. The minified output for the usual color: red and (min-width: 600px) does not change. Only the rare color : red style now keeps one space (color :red), which is still valid CSS.

The new preserve descendant combinator before pseudo-class case in src/helper/css/index.test.tsx fails on main with .css-123{&:first-child{margin:0}&:hover:is(h1,h2){color:red}} and passes with this change. vp test --project main passes (123 files), and tsc -p tsconfig.spec.json and vp check are clean.

The author should do the following, if applicable

• Add tests
• Run tests
• pnpm run check:fix to format and lint the code
• Add TSDoc/JSDoc to document the code (no public API change)

🤖 Generated with Claude Code