✨ feat(sidebar): 新增 Sidebar 慢 SQL 历史浮动入口

- 新建 SlowQueryRailButton：独立小组件，从 store 直接读 tabs/connections 解析激活连接
- 挂载方式：浮动在 Sidebar 右下角，不修改 Sidebar.tsx 内部代码（避免改 10275 行的大文件）
- 体验优化：无激活连接时按钮自动禁用并 tooltip 提示；与 Ctrl+Shift+L 快捷键路径并存
- bundle 保持：SlowQueryPanel 继续走 lazy 加载独立 chunk，不进入主 bundle

frontend/src/App.tsx

@@ -4,6 +4,7 @@ import { Layout, Button, ConfigProvider, theme, message, Spin, Slider, Progress,
 import { PlusOutlined, ConsoleSqlOutlined, UploadOutlined, DownloadOutlined, CloudDownloadOutlined, BugOutlined, ToolOutlined, GlobalOutlined, InfoCircleOutlined, GithubOutlined, SkinOutlined, CheckOutlined, MinusOutlined, BorderOutlined, CloseOutlined, SettingOutlined, LinkOutlined, BgColorsOutlined, AppstoreOutlined, RobotOutlined, FolderOpenOutlined, HddOutlined, SafetyCertificateOutlined, SwitcherOutlined, CodeOutlined, RightOutlined } from '@ant-design/icons';
 import { BrowserOpenURL, Environment, EventsOn, Quit, WindowFullscreen, WindowGetPosition, WindowGetSize, WindowIsFullscreen, WindowIsMaximised, WindowIsMinimised, WindowIsNormal, WindowMaximise, WindowMinimise, WindowSetPosition, WindowSetSize, WindowUnfullscreen, WindowUnmaximise } from '../wailsjs/runtime';
 import Sidebar from './components/Sidebar';
+import SlowQueryRailButton from './components/sidebar/SlowQueryRailButton';
 import TabManager from './components/TabManager';
 import ConnectionModal from './components/ConnectionModal';
 import SnippetSettingsModal from './components/SnippetSettingsModal';
@@ -3692,6 +3693,18 @@ function App() {
                             onFocusCommandSearch={handleFocusSidebarSearch}
                         />
                     </div>
+                    {/* 慢 SQL 历史入口：浮动在 Sidebar 右下角，独立组件不依赖 Sidebar 内部 state */}
+                    <SlowQueryRailButton
+                        style={{
+                            position: 'absolute',
+                            right: 8,
+                            bottom: isV2Ui ? 8 : 66,
+                            zIndex: 10,
+                            background: 'var(--gn-card-bg, rgba(255,255,255,0.9))',
+                            borderRadius: 6,
+                            boxShadow: '0 1px 4px rgba(0,0,0,0.1)',
+                        }}
+                    />
                     {!connectionWorkbenchState.ready && (
                         <div
                             style={{

frontend/src/components/sidebar/SlowQueryRailButton.tsx

@@ -0,0 +1,99 @@
+import { lazy, Suspense, useMemo, useState } from 'react'
+import { Tooltip } from 'antd'
+import { HistoryOutlined } from '@ant-design/icons'
+import { useStore } from '../../store'
+import type { ConnectionConfig } from '../../types'
+// lazy 加载避免 SlowQueryPanel（react-flow + dagre 约 200KB）进入主 bundle
+const SlowQueryPanel = lazy(() => import('../explain/SlowQueryPanel'))
+
+// Sidebar 顶部的慢 SQL 历史入口。
+//
+// 设计要点：
+//   - 完全独立组件，不依赖 Sidebar.tsx 内部 state（避免改 Sidebar Props）
+//   - 自己从 store 读取 tabs/connections，解析当前激活 tab 的连接配置
+//   - 通过 lazy import SlowQueryPanel（react-flow/dagre 不进入主 bundle）
+//   - 没有激活的连接时按钮禁用，hover 给提示
+//
+// 挂载位置：由调用方决定（App.tsx 把它放在 Sidebar 容器内）
+
+interface SlowQueryRailButtonProps {
+  /** 自定义 className 用于外层定位 */
+  className?: string
+  /** 自定义 style（用于绝对定位到 Sidebar 角落） */
+  style?: React.CSSProperties
+}
+
+export default function SlowQueryRailButton({ className, style }: SlowQueryRailButtonProps) {
+  const [open, setOpen] = useState(false)
+  const tabs = useStore(s => s.tabs)
+  const activeTabId = useStore(s => s.activeTabId)
+  const connections = useStore(s => s.connections)
+
+  // 解析当前激活 tab 的 ConnectionConfig
+  const activeConfig = useMemo<ConnectionConfig | null>(() => {
+    if (!activeTabId) return null
+    const tab = tabs.find(t => t.id === activeTabId)
+    if (!tab?.connectionId) return null
+    const conn = connections.find(c => c.id === tab.connectionId)
+    if (!conn) return null
+    return {
+      ...conn.config,
+      port: Number(conn.config.port),
+      password: conn.config.password || '',
+      database: conn.config.database || '',
+      useSSH: conn.config.useSSH || false,
+      ssh: conn.config.ssh || { host: '', port: 22, user: '', password: '', keyPath: '' },
+    } as ConnectionConfig
+  }, [tabs, activeTabId, connections])
+
+  const activeTab = tabs.find(t => t.id === activeTabId)
+  const dbName = activeTab?.dbName || ''
+
+  const buttonDisabled = !activeConfig
+  const tooltipText = buttonDisabled
+    ? '请先打开一个数据库连接的查询标签'
+    : '查看当前连接的慢 SQL 历史（Ctrl+Shift+L）'
+
+  return (
+    <>
+      <Tooltip title={tooltipText} placement="right">
+        <button
+          type="button"
+          className={className}
+          onClick={() => !buttonDisabled && setOpen(true)}
+          disabled={buttonDisabled}
+          style={{
+            display: 'flex',
+            alignItems: 'center',
+            justifyContent: 'center',
+            width: 32,
+            height: 32,
+            border: 'none',
+            background: 'transparent',
+            cursor: buttonDisabled ? 'not-allowed' : 'pointer',
+            color: buttonDisabled
+              ? 'var(--gn-text-muted, #adb5bd)'
+              : 'var(--gn-text, #495057)',
+            opacity: buttonDisabled ? 0.5 : 1,
+            transition: 'opacity 0.15s, color 0.15s',
+            ...style,
+          }}
+          aria-label="慢 SQL 历史"
+        >
+          <HistoryOutlined style={{ fontSize: 16 }} />
+        </button>
+      </Tooltip>
+
+      {open && activeConfig && (
+        <Suspense fallback={null}>
+          <SlowQueryPanel
+            open={open}
+            onClose={() => setOpen(false)}
+            config={activeConfig}
+            dbName={dbName}
+          />
+        </Suspense>
+      )}
+    </>
+  )
+}