fix(web): stabilize realtime chat list synchronization

- throttle chat list reload on realtime events

- refresh chat previews after incoming messages

- keep active chat messages in sync on chat_updated

web/src/hooks/useRealtime.ts

@@ -23,6 +23,7 @@ export function useRealtime() {
   const reconnectAttemptsRef = useRef(0);
   const manualCloseRef = useRef(false);
   const notificationPermissionRequestedRef = useRef(false);
+  const reloadChatsTimerRef = useRef<number | null>(null);
 
   const wsUrl = useMemo(() => {
     return accessToken ? buildWsUrl(accessToken) : null;
@@ -108,13 +109,15 @@ export function useRealtime() {
             maybeShowBrowserNotification(chatId, message, chatStore.activeChatId);
           }
           if (!chatStore.chats.some((chat) => chat.id === chatId)) {
-            void chatStore.loadChats();
+            scheduleReloadChats();
+          } else {
+            scheduleReloadChats();
           }
         }
         if (event.event === "chat_updated") {
           const chatId = Number(event.payload.chat_id);
           if (Number.isFinite(chatId)) {
-            void chatStore.loadChats();
+            scheduleReloadChats();
             if (chatStore.activeChatId === chatId) {
               void chatStore.loadMessages(chatId);
             }
@@ -223,6 +226,10 @@ export function useRealtime() {
         window.clearTimeout(reconnectTimeoutRef.current);
         reconnectTimeoutRef.current = null;
       }
+      if (reloadChatsTimerRef.current !== null) {
+        window.clearTimeout(reloadChatsTimerRef.current);
+        reloadChatsTimerRef.current = null;
+      }
       wsRef.current?.close();
       wsRef.current = null;
       typingByChat.current = {};
@@ -230,6 +237,16 @@ export function useRealtime() {
     };
   }, [wsUrl, meId]);
 
+  function scheduleReloadChats() {
+    if (reloadChatsTimerRef.current !== null) {
+      return;
+    }
+    reloadChatsTimerRef.current = window.setTimeout(() => {
+      reloadChatsTimerRef.current = null;
+      void useChatStore.getState().loadChats();
+    }, 250);
+  }
+
   return null;
 }