feat(dashboard): scroll selected autocomplete item into view

Closes bd-4lc. When navigating with arrow keys, the selected item now
scrolls into view using scrollIntoView({ block: 'nearest' }) to prevent
jarring scrolls when item is already visible.

dashboard/components/SimpleInput.js

@@ -89,6 +89,17 @@ export function SimpleInput({ sessionId, status, onRespond, autocompleteConfig =
     return () => document.removeEventListener('mousedown', handleClickOutside);
   }, [showAutocomplete]);
 
+  // Scroll selected item into view when navigating with arrow keys
+  useEffect(() => {
+    if (showAutocomplete && autocompleteRef.current) {
+      const container = autocompleteRef.current;
+      const selectedEl = container.children[selectedIndex];
+      if (selectedEl) {
+        selectedEl.scrollIntoView({ block: 'nearest' });
+      }
+    }
+  }, [selectedIndex, showAutocomplete]);
+
   // Insert a selected skill into the text
   const insertSkill = useCallback((skill) => {
     if (!triggerInfo || !autocompleteConfig) return;