fix(chat): hydrate user avatar after auth restore

src/providers/root-providers.tsx

@@ -7,6 +7,7 @@
  *   AuthProvider → UserProvider → SidebarProvider → ChatProvider
  *   + AuthStatusChecker（启动时一次：派发 AuthInit）
  *   + OAuthSessionSync   （持续监听 NextAuth session → auth machine）
+ *   + UserAuthSync       （auth 登录态恢复后 hydrate user machine）
  *
  * 它们始终挂载，保证各页面直接 `use*State()` / `use*Dispatch()` 即可，
  * 无需在每个页面单独包裹。
@@ -19,6 +20,7 @@ import { AuthStatusChecker } from "@/stores/auth/auth-status-checker";
 import { OAuthSessionSync } from "@/stores/auth/oauth-session-sync";
 import { ChatProvider } from "@/stores/chat/chat-context";
 import { SidebarProvider } from "@/stores/sidebar/sidebar-context";
+import { UserAuthSync } from "@/stores/user/user-auth-sync";
 import { UserProvider } from "@/stores/user/user-context";
 
 export interface RootProvidersProps {
@@ -34,6 +36,7 @@ export function RootProviders({ children }: RootProvidersProps) {
       {/* OAuthSessionSync 同样依赖 AuthProvider 上下文 */}
       <OAuthSessionSync />
       <UserProvider>
+        <UserAuthSync />
         <SidebarProvider>
           <ChatProvider>
             {children}

src/stores/user/user-auth-sync.tsx

@@ -0,0 +1,34 @@
+"use client";
+
+/**
+ * Auth → User 启动同步器
+ *
+ * AuthStatusChecker 只负责恢复 loginStatus；头像等登录用户资料由
+ * UserStorage 持久化在 user machine 这一侧。冷启动直达 /chat 时，
+ * 没有经过 splash/auth 的跳转副作用，因此需要在登录态恢复后主动
+ * hydrate user store。
+ */
+import { useEffect, useRef } from "react";
+
+import { useAuthState } from "@/stores/auth/auth-context";
+
+import { useUserDispatch } from "./user-context";
+
+export function UserAuthSync() {
+  const { loginStatus } = useAuthState();
+  const userDispatch = useUserDispatch();
+  const lastInitializedStatusRef = useRef<string | null>(null);
+
+  useEffect(() => {
+    if (loginStatus === "notLoggedIn" || loginStatus === "guest") {
+      lastInitializedStatusRef.current = null;
+      return;
+    }
+
+    if (lastInitializedStatusRef.current === loginStatus) return;
+    lastInitializedStatusRef.current = loginStatus;
+    userDispatch({ type: "UserInit" });
+  }, [loginStatus, userDispatch]);
+
+  return null;
+}