fix: 修复登出按钮无效 — 同时清除磁盘 cookie 和浏览器内存 context

- BrowserManager 新增 clearContext() 方法，关闭并丢弃平台 context
- deleteCookies 同时调用 cookieStore.delete + browser.clearContext
- 前端登出后直接 resetStatus，不再触发浏览器请求检查状态

src/browser/manager.ts

@@ -193,6 +193,21 @@ export class BrowserManager {
     logger.debug({ platform }, 'Cookies saved');
   }
 
+  /**
+   * Close and discard the browser context for a platform so the next
+   * operation creates a fresh one (without any cookies or storage).
+   */
+  async clearContext(platform: string): Promise<void> {
+    const ctx = this.contexts.get(platform);
+    if (!ctx) return;
+
+    this.contexts.delete(platform);
+    await ctx.close().catch((err: unknown) => {
+      logger.warn({ err, platform }, 'Error closing context during clearContext');
+    });
+    logger.info({ platform }, 'Browser context cleared');
+  }
+
   /**
    * Wait for every in-flight platform queue to settle. Useful during
    * graceful shutdown so that running operations finish before teardown.