- Introduce `.btn-icon-sm` (28×28, 18 px icon) in `_buttons.scss` for
  a miniature icon-button variant.
- Remove `.btn-secondary` from demo copy buttons so they render as
  transparent icon-only controls without background.
- Add `size` prop to `GnIconButton` and `GnCopyButton` Vue components.
- Update docs and demo to reflect the new size option.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>