refactor(vscode-ide-companion): reorganize component structure

重构组件结构，优化目录组织：
- 将 ChatHeader 从 ui/ 移动到 layouts/ 目录
- 删除未使用的 Button 和 Card 组件
- 更新 tailwind.config.js 扫描路径为 layouts/
- 简化组件目录结构，提高可维护性

packages/vscode-ide-companion/src/webview/components/layouts/ChatHeader.tsx

@@ -0,0 +1,109 @@
+/**
+ * @license
+ * Copyright 2025 Qwen Team
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import type React from 'react';
+
+interface ChatHeaderProps {
+  currentSessionTitle: string;
+  onLoadSessions: () => void;
+  onSaveSession: () => void;
+  onNewSession: () => void;
+}
+
+export const ChatHeader: React.FC<ChatHeaderProps> = ({
+  currentSessionTitle,
+  onLoadSessions,
+  onSaveSession: _onSaveSession,
+  onNewSession,
+}) => (
+  <div
+    className="flex gap-1 select-none py-1.5 px-2.5"
+    style={{
+      borderBottom: '1px solid var(--app-primary-border-color)',
+      backgroundColor: 'var(--app-header-background)',
+    }}
+  >
+    {/* Past Conversations Button */}
+    <button
+      className="flex-none py-1 px-2 bg-transparent border border-transparent rounded cursor-pointer flex items-center justify-center outline-none font-medium transition-colors duration-200 hover:bg-[var(--app-ghost-button-hover-background)] focus:bg-[var(--app-ghost-button-hover-background)]"
+      style={{
+        borderRadius: 'var(--corner-radius-small)',
+        color: 'var(--app-primary-foreground)',
+        fontSize: 'var(--vscode-chat-font-size, 13px)',
+      }}
+      onClick={onLoadSessions}
+      title="Past conversations"
+    >
+      <span className="flex items-center gap-1">
+        <span style={{ fontSize: 'var(--vscode-chat-font-size, 13px)' }}>
+          {currentSessionTitle}
+        </span>
+        <svg
+          xmlns="http://www.w3.org/2000/svg"
+          viewBox="0 0 20 20"
+          fill="currentColor"
+          aria-hidden="true"
+          className="w-3.5 h-3.5"
+        >
+          <path
+            fillRule="evenodd"
+            d="M5.22 8.22a.75.75 0 0 1 1.06 0L10 11.94l3.72-3.72a.75.75 0 1 1 1.06 1.06l-4.25 4.25a.75.75 0 0 1-1.06 0L5.22 9.28a.75.75 0 0 1 0-1.06Z"
+            clipRule="evenodd"
+          ></path>
+        </svg>
+      </span>
+    </button>
+
+    {/* Spacer */}
+    <div className="flex-1"></div>
+
+    {/* Save Session Button */}
+    {/* <button
+        className="flex-none p-0 bg-transparent border border-transparent rounded cursor-pointer flex items-center justify-center outline-none w-6 h-6 hover:bg-[var(--app-ghost-button-hover-background)] focus:bg-[var(--app-ghost-button-hover-background)]"
+        style={{
+          color: 'var(--app-primary-foreground)',
+        }}
+        onClick={onSaveSession}
+        title="Save Conversation"
+      >
+        <svg
+          xmlns="http://www.w3.org/2000/svg"
+          viewBox="0 0 20 20"
+          fill="currentColor"
+          aria-hidden="true"
+          data-slot="icon"
+          className="w-4 h-4"
+        >
+          <path
+            fillRule="evenodd"
+            d="M4.25 2A2.25 2.25 0 0 0 2 4.25v11.5A2.25 2.25 0 0 0 4.25 18h11.5A2.25 2.25 0 0 0 18 15.75V8.25a.75.75 0 0 1 .217-.517l.083-.083a.75.75 0 0 1 1.061 0l2.239 2.239A.75.75 0 0 1 22 10.5v5.25a4.75 4.75 0 0 1-4.75 4.75H4.75A4.75 4.75 0 0 1 0 15.75V4.25A4.75 4.75 0 0 1 4.75 0h5a.75.75 0 0 1 0 1.5h-5ZM9.017 6.5a1.5 1.5 0 0 1 2.072.58l.43.862a1 1 0 0 0 .895.558h3.272a1.5 1.5 0 0 1 1.5 1.5v6.75a1.5 1.5 0 0 1-1.5 1.5h-7.5a1.5 1.5 0 0 1-1.5-1.5v-6.75a1.5 1.5 0 0 1 1.5-1.5h1.25a1 1 0 0 0 .895-.558l.43-.862a1.5 1.5 0 0 1 .511-.732ZM11.78 8.47a.75.75 0 0 0-1.06-1.06L8.75 9.379 7.78 8.41a.75.75 0 0 0-1.06 1.06l1.5 1.5a.75.75 0 0 0 1.06 0l2.5-2.5Z"
+            clipRule="evenodd"
+          ></path>
+        </svg>
+      </button> */}
+
+    {/* New Session Button */}
+    <button
+      className="flex-none p-0 bg-transparent border border-transparent rounded cursor-pointer flex items-center justify-center outline-none w-6 h-6 hover:bg-[var(--app-ghost-button-hover-background)] focus:bg-[var(--app-ghost-button-hover-background)]"
+      style={{
+        color: 'var(--app-primary-foreground)',
+      }}
+      onClick={onNewSession}
+      title="New Session"
+    >
+      <svg
+        xmlns="http://www.w3.org/2000/svg"
+        viewBox="0 0 20 20"
+        fill="currentColor"
+        aria-hidden="true"
+        data-slot="icon"
+        className="w-4 h-4"
+      >
+        <path d="M10.75 4.75a.75.75 0 0 0-1.5 0v4.5h-4.5a.75.75 0 0 0 0 1.5h4.5v4.5a.75.75 0 0 0 1.5 0v-4.5h4.5a.75.75 0 0 0 0-1.5h-4.5v-4.5Z"></path>
+      </svg>
+    </button>
+  </div>
+);