.auto-contrast      { position:relative; }
.auto-contrast .content,
.auto-contrast > *:not(img) {              /* genérico p/ blocos Gutenberg */
  position:relative; z-index:2;            /* fica acima do véu */
}

.auto-contrast.light .content,
.auto-contrast.light > * { color:#222; text-shadow:0 0 4px rgba(255,255,255,.6); }
.auto-contrast.dark  .content,
.auto-contrast.dark  > * { color:#fff; text-shadow:0 0 4px rgba(0,0,0,.6); }

/* véu opcional garantidor de contraste */
.auto-contrast::after {
  content:""; position:absolute; inset:0; pointer-events:none;
  transition:background .3s;
}
.auto-contrast.light::after { background:rgba(255,255,255,.35); }
.auto-contrast.dark::after  { background:rgba(0,0,0,.35); }