fix: use window.addEventListener for dropdown keyboard nav

inputRef-based listener never fired (ref null at effect time or
element-level listeners don't catch events in this React setup).
Switched to window.addEventListener matching the pattern every other
keyboard handler in this codebase already uses.

web/src/components/ChatArea.tsx

@@ -495,10 +495,8 @@ export function ChatArea() {
     inputEl.setSelectionRange(pos, pos);
   };
 
-  // ponytail: stable keydown handler via addEventListener avoids stale closure issues
+  // ponytail: window listener matches existing pattern in codebase (CommandDropdown, modals)
   useEffect(() => {
-    const el = inputRef.current;
-    if (!el) return;
     const handler = (e: KeyboardEvent) => {
       if (e.ctrlKey && e.key === 'e') {
         e.preventDefault();
@@ -568,8 +566,8 @@ export function ChatArea() {
         setDropdownIndex(0);
       }
     };
-    el.addEventListener('keydown', handler);
-    return () => el.removeEventListener('keydown', handler);
+    window.addEventListener('keydown', handler);
+    return () => window.removeEventListener('keydown', handler);
   }, [members, currentUser, activeChannelId, sendMessage, replyToMessage, handleMentionSelect]);
 
   const handleSubmit = async (event: React.FormEvent) => {