/**
 * Design 2026 — Plain (self-hosted in /fonts)
 * Loaded on pages using 2026 header/footer (see si_uses_design_2026()).
 *
 * @font-face rules are output via si_plain_font_faces_2026_css() in functions.php
 * so URLs always resolve to the theme directory (even when CSS is cached/merged).
 */