fix(react): close three useChat gaps surfaced by PR #5 review

- send(): sync messagesRef before runStream so rapid synchronous sends
  both reach the outgoing request body
- useState init: hydrate pendingDecisions from initialMessages so
  rehydrated paused tool calls render decision UI immediately
- unmount: abort the in-flight fetch on cleanup to prevent leaked
  streams when the consumer unmounts mid-request

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: yyyyaaa

packages/react/src/use-chat.ts

@@ -94,7 +94,7 @@ export function useChat(options: UseChatOptions): UseChatResult {
   const [isStreaming, setIsStreaming] = useState(false);
   const [pendingDecisions, setPendingDecisions] = useState<
     ReadonlyMap<string, ToolDecisionPendingEvent>
-  >(() => new Map());
+  >(() => rederivePendingDecisions(options.initialMessages ?? []));
   const [executingToolCallIds, setExecutingToolCallIds] = useState<ReadonlySet<string>>(
     () => new Set()
   );
@@ -293,6 +293,7 @@ export function useChat(options: UseChatOptions): UseChatResult {
       const userMessage: Message =
         typeof input === 'string' ? createUserMessage(input) : input;
       const requestMessages = [...messagesRef.current, userMessage];
+      messagesRef.current = requestMessages;
       await runStream(requestMessages, userMessage);
     },
     [runStream]
@@ -358,6 +359,13 @@ export function useChat(options: UseChatOptions): UseChatResult {
     []
   );
 
+  useEffect(() => {
+    return () => {
+      abortControllerRef.current?.abort();
+      abortControllerRef.current = null;
+    };
+  }, []);
+
   const abort = useCallback(() => {
     abortControllerRef.current?.abort();
     abortControllerRef.current = null;