Fix label text splitting across multiple lines
CSS grid makes every direct child a separate grid item, so inline
elements like <sub> within label text were stacking vertically instead
of rendering inline. Wrap label text in <span class="lbl"> to group
all inline content into a single grid item, and add white-space: nowrap
to prevent long labels from wrapping.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>