style(web): 移除顶栏 AI 快捷操作区并优化差旅领导意见事件样式

- TopBar 移除 AI 模式下的公司切换/AI 模式切换快捷操作块及 showAiModeUtilityActions 计算属性，清理 top-bar.css 对应样式
- TravelRequestDetailView 领导意见事件重构为状态/意见/审批人结构化布局，travel-request-detail-view.css 补充对应样式
- 同步更新 topbar-ai-mode-switch、ai-sidebar-rail-mode、travel-request-detail-leader-approval 测试

web/tests/ai-sidebar-rail-mode.test.mjs

@@ -44,7 +44,7 @@ test('workbench AI mode swaps the traditional rail for the AI three-layer rail',
   assert.match(appShell, /function openAiSidebarNewChat\(\)/)
   assert.match(appShell, /function openAiSidebarRecent\(item = \{\}\)/)
   assert.match(appShell, /function handleAiConversationRename\(payload = \{\}\)/)
-  assert.match(appShell, /import \{ computed, nextTick, onBeforeUnmount, onMounted, ref, watch \} from 'vue'/)
+  assert.match(appShell, /import \{ computed, nextTick, ref, watch \} from 'vue'/)
   assert.match(appShell, /async function openAiConversationWorkspace\(type, payload = null\)/)
   assert.match(appShell, /const navigation = handleNavigate\('workbench'\)/)
   assert.match(appShell, /if \(navigation && typeof navigation\.then === 'function'\)[\s\S]*await navigation/)