Remove preventScroll from crossword cell focus

preventScroll was blocking the viewport from scrolling to the grid cell
when a clue was clicked from the sidebar. The clue list overflow fix is
sufficient to contain scrollIntoView without needing preventScroll.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

public/app.js

@@ -1117,7 +1117,7 @@ async function openCrossword(itemId) {
     const key = `${r},${c}`;
     if (!cells[key]) return;
     selectCell(key);
-    cells[key].input.focus({ preventScroll: true });
+    cells[key].input.focus();
   }
 
   // Wire up cells