feat(chat): implement pull-to-refresh functionality and pagination for chat history

src/stores/chat/chat-context.tsx

@@ -23,6 +23,8 @@ interface ChatState {
   upgradeReason: MachineContext["upgradeReason"];
   /** history 初始加载完成标志（local → network → save 跑完） —— UI 可用此显示 loading */
   historyLoaded: boolean;
+  hasMoreHistory: boolean;
+  isLoadingMoreHistory: boolean;
   unlockHistoryPromptVisible: boolean;
   lockedHistoryCount: number;
   isUnlockingHistory: boolean;
@@ -76,6 +78,10 @@ function selectChatState(state: ChatSnapshot): SelectedChatState {
     upgradePromptVisible: state.context.upgradePromptVisible,
     upgradeReason: state.context.upgradeReason,
     historyLoaded: state.context.historyLoaded,
+    hasMoreHistory:
+      state.context.historyLoaded &&
+      state.context.nextHistoryOffset < state.context.historyTotal,
+    isLoadingMoreHistory: state.context.isLoadingMoreHistory,
     unlockHistoryPromptVisible: state.context.unlockHistoryPromptVisible,
     lockedHistoryCount: state.context.lockedHistoryCount,
     isUnlockingHistory: state.context.isUnlockingHistory,