CSS minifier incorrectly removes leading & nesting selector #4497

The CSS minifier removes a leading & from nested selectors that also use & within other selector parts like :not(), which incorrectly changes the overall selector's meaning.

Reproduction: esbuild playground

Input:

.a {
  .b:not(.a .b .b) {
    --level: 1;

    & .b:not(& .b .b) {
      --level: 2;

      & .b:not(& .b .b) {
        --level: 3;
      }
    }
  }
}

Output with esbuild 0.28.1 and --loader=css --minify:

.a{.b:not(.a .b .b){--level:1;.b:not(& .b .b){--level:2;.b:not(& .b .b){--level:3}}}}

The leading & before each nested .b:not(...) selector must be preserved, or the output must be rewritten to an equivalent selector. In the example above, given three nested .b elements, the input computes --level as 1, 2, and 3, while the minified output computes 3 for all three elements.