Scrolling text: 'side edges' mode with characters stacked vertically on both borders

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/control.html

@@ -257,6 +257,7 @@
           <option value="h">➡️ Orizzontale</option>
           <option value="vup">⬆️ Verticale (su)</option>
           <option value="vdown">⬇️ Verticale (giù)</option>
+          <option value="sides">↕️ Bordi laterali (caratteri impilati)</option>
         </select>
         <label>Velocità testo <span id="ticker-speed-val">1.0×</span></label>
         <input type="range" id="ticker-speed" min="0.2" max="4" step="0.1" value="1" />