Generate `:is(<group> &)` instead of `&:is(<group> *)` (and the `~`
equivalent for `peer-*`). The target now sits in the subject position, so
browsers can limit style invalidation to the elements that carry the utility
instead of every descendant or following sibling of the group/peer.
Matching behavior and specificity are unchanged. The outer `:is(…)` keeps
compound variants such as `has-group-*` behaving the same.
The one accepted difference: with a default `@namespace`, compound variants
such as `group-group-*` no longer restrict the target to that namespace.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
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