feat: header 增加当前会话总 token 消耗统计

- 新增 totalTokens 元素（帮助按钮右侧，🪙 图标 + 数字）
- chat-area.ts 新增 updateTotalTokens() 函数
- 四个触发点：新消息完成、新建会话、加载历史、应用初始化
- 数字自动格式化（toLocaleString）

src/renderer/components/chat-area.ts

@@ -384,6 +384,18 @@ export function enableAutoScroll(): void {
   if (scrollBtnEl) scrollBtnEl.style.display = 'none';
 }
 
+/** 统计当前会话总 token 消耗并更新 header 显示 */
+export function updateTotalTokens(): void {
+  const session = state.get<ChatSession | null>(KEYS.CURRENT_SESSION);
+  const el = document.querySelector('#totalTokensValue');
+  if (!el) return;
+  if (!session) { el.textContent = '0'; return; }
+  const total = session.messages
+    .filter(m => m.role === 'assistant' && m.eval_count)
+    .reduce((sum, m) => sum + (m.eval_count || 0), 0);
+  el.textContent = total > 0 ? total.toLocaleString() : '0';
+}
+
 // ── 导出功能 ──
 
 async function nativeSaveFile(defaultName: string, content: string): Promise<void> {

src/renderer/components/history-modal.ts

@@ -4,7 +4,7 @@
 
 import { state, KEYS } from '../state/state.js';
 import { debounce, escapeHtml, formatTime } from '../utils/utils.js';
-import { exportAsMarkdown, exportAsHtml, exportAsTxt, renderMessages, clearMessages } from './chat-area.js';
+import { exportAsMarkdown, exportAsHtml, exportAsTxt, renderMessages, clearMessages, updateTotalTokens } from './chat-area.js';
 import { showConfirm } from './prompt-modal.js';
 import { ChatDB } from '../db/chat-db.js';
 import { logSession, logWarn } from '../services/log-service.js';
@@ -181,6 +181,7 @@ async function loadHistorySession(sessionId: string): Promise<void> {
 
   clearMessages();
   renderMessages();
+  updateTotalTokens();
   closeHistoryModal();
 }
 

src/renderer/components/input-area.ts

@@ -7,7 +7,7 @@ import { detectLanguage, truncate, escapeHtml, formatSize } from '../utils/utils
 import { getSelectedModel, isThinkEnabled, isVisionAvailable, isToolCallingSupported } from './model-bar.js';
 import {
   renderMessages, appendAssistantPlaceholder, appendSystemMessage,
-  updateLastAssistantMessage, clearMessages, safeMarkdown, enableAutoScroll
+  updateLastAssistantMessage, clearMessages, safeMarkdown, enableAutoScroll, updateTotalTokens
 } from './chat-area.js';
 import { showToast } from './toast.js';
 import { isRagEnabled, performRagRetrieval } from './kb-modal.js';
@@ -521,6 +521,7 @@ export async function sendMessage(): Promise<void> {
     }
 
     await saveCurrentSession();
+    updateTotalTokens();
 
     // ── 自动提取记忆（非阻塞）──
     if (isMemoryEnabled() && freshSession.messages.length >= 6) {
@@ -738,6 +739,7 @@ async function sendMessageWithAgentLoop(text: string, currentSession: ChatSessio
         updateLastAssistantMessage(assistantContent, thinkContent || null, loopStats || null);
         renderMessages();
         await saveCurrentSession();
+        updateTotalTokens();
       }
     });
   } catch (err) {