fix: preserve whitespace before a * namespace in attribute selectors

[spokodev]

Problem

Leading whitespace before a * (universal) namespace in an attribute selector is dropped on a round-trip, while it is preserved for a named namespace or no namespace:

const parser = require("postcss-selector-parser");
const rt = (s) => { let o; parser((r) => (o = r.toString())).processSync(s); return o; };

rt("[ *|a ]");  // "[*|a ]"   ← leading space lost
rt("[ ns|a ]"); // "[ ns|a ]" (ok)
rt("[ |a ]");   // "[ |a ]"   (ok)
rt("[ a ]");    // "[ a ]"    (ok)

Root cause

In attribute(), the tokens.asterisk branch records the raw spacing with the wrong variable:

if (spaceBefore) {
  node.spaces.attribute.before = spaceBefore;
  spaceBefore = "";          // cleared here
}
if (commentBefore) {
  node.raws.spaces.attribute.before = spaceBefore;  // ← always "" now
  commentBefore = "";
}

spaceBefore has already been set to "", so raws.spaces.attribute.before is emptied. Since toString prefers the raw spacing when present, the leading whitespace disappears. The tokens.word branch right below does the same thing correctly with commentBefore.

Fix

Use commentBefore for the raw spacing, matching the word-namespace branch (one word).

Test plan

• Added an attribute test for a universal namespace with surrounding spaces ([ *|bar ]); the tree was already correct, but the toString round-trip failed on main and passes with the fix.
• A round-trip property check over generated selectors flagged this case; the fix clears it with no regressions. Full suite green (779), eslint/tsc clean.