feat(web): 工作台 AI 模式与差旅/风险建议交互优化

- 新增 PersonalWorkbenchAiMode 组件、AI 侧边栏与 orb 机器人视觉资源
- 新增 aiApplicationDraftModel / aiExpenseDraftModel / aiWorkbenchConversationStore
  及业务准入 aiSidebarBusinessAccess，支撑 AI 模式下的申请与报销草稿
- 顶栏、侧边栏、工作台样式重构，适配 AI 模式切换与响应式布局
- 同步 steward plan/off_topic、差旅报销引导流、风险建议卡片等测试

web/src/assets/styles/app.css

@@ -15,7 +15,7 @@
 }
 
 .app {
-  --sidebar-expanded-width: 184px;
+  --sidebar-expanded-width: 304px;
   --sidebar-collapsed-width: 64px;
   --sidebar-motion: 220ms cubic-bezier(0.4, 0, 0.2, 1);
 
@@ -43,8 +43,8 @@
 }
 
 .app.sidebar-collapsed .app-sidebar {
-  flex-basis: var(--sidebar-collapsed-width);
   width: var(--sidebar-collapsed-width);
+  flex-basis: var(--sidebar-collapsed-width);
   overflow: visible;
   z-index: 200;
 }
@@ -54,6 +54,19 @@
   z-index: 1;
 }
 
+.sidebar-mode-fade-enter-active,
+.sidebar-mode-fade-leave-active {
+  transition:
+    opacity 180ms var(--ease),
+    transform 180ms var(--ease);
+}
+
+.sidebar-mode-fade-enter-from,
+.sidebar-mode-fade-leave-to {
+  opacity: 0;
+  transform: translateX(-8px);
+}
+
 .app > .main {
   flex: 1 1 auto;
   min-width: 0;
@@ -133,7 +146,7 @@
   color: var(--theme-primary-active);
   font-size: 12px;
   font-weight: 800;
-  letter-spacing: 0.12em;
+  letter-spacing: 0;
 }
 
 .boot-badge-error {
@@ -217,6 +230,10 @@
   background-size: 100% 100%, 100% 100%, 32px 32px, 32px 32px;
   background-attachment: local;
 }
+.workarea.workbench-workarea.workbench-workarea-ai-mode {
+  padding: 0;
+  background: transparent;
+}
 .workarea.settings-workarea {
   padding: 0;
   background: #fff;
@@ -312,6 +329,7 @@
   }
 
   .workarea.workbench-workarea { overflow: auto; padding: 16px; }
+  .workarea.workbench-workarea.workbench-workarea-ai-mode { padding: 0; }
 
   .mobile-overlay {
     position: fixed;