Chip metrics move from fixed pixels to em - text, icons, padding, gap,
radius, and the dismiss button all track the surrounding font, so the
pills match the text at any prompt size. The chat variant pins the
original 12px, where every em value resolves to the same pixels as
before, and the skill glyph fills its em-sized span instead of a
hardcoded 14px box.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>