Fix crossword clue scrollIntoView jumping the page

Replace scrollIntoView (which escapes to the window when the list isn't
tall enough to scroll) with manual scrollTop logic that stays strictly
within the clue list container.

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

public/app.js

@@ -1090,7 +1090,16 @@ async function openCrossword(itemId) {
     }
     const listEl = dir === 'across' ? acrossListEl : downListEl;
     const li = listEl.querySelector(`[data-num="${word.num}"]`);
-    if (li) { li.classList.add('selected-clue'); li.scrollIntoView({ block: 'nearest' }); }
+    if (li) {
+      li.classList.add('selected-clue');
+      const liTop = li.offsetTop;
+      const liBottom = liTop + li.offsetHeight;
+      if (liBottom > listEl.scrollTop + listEl.clientHeight) {
+        listEl.scrollTop = liBottom - listEl.clientHeight;
+      } else if (liTop < listEl.scrollTop) {
+        listEl.scrollTop = liTop;
+      }
+    }
   }
 
   function pickWord(key) {