fix(ui): prevent chat submit during IME composition

Check e.nativeEvent.isComposing so pressing Enter to confirm
CJK input does not accidentally submit the message.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

packages/ui/src/components/chat-input.tsx

@@ -33,7 +33,7 @@ export function ChatInput({ onSubmit, disabled }: ChatInputProps) {
           e.target.style.height = `${Math.min(e.target.scrollHeight, 200)}px`;
         }}
         onKeyDown={(e) => {
-          if (e.key === "Enter" && !e.shiftKey) {
+          if (e.key === "Enter" && !e.shiftKey && !e.nativeEvent.isComposing) {
             e.preventDefault();
             handleSubmit();
           }