feat(admin-web): surface generation error message and speed up active polling

Hoists hasActiveGenerationStatus into the shared display helper so all
views agree on what counts as in-flight generation, shows the backend
generation_error_message inline on the imitation list and detail drawer
when status is failed, and drops the workspace/templates/imitation poll
interval from 10s to 3s (with a 5s fallback when streaming is enabled)
plus explicit query-cache invalidation so failed/completed states show
up promptly.

apps/admin-web/src/components/ArticleDetailDrawer.vue

@@ -20,6 +20,7 @@ import {
   getGenerateStatusMeta,
   getPublishStatusMeta,
   getSourceTypeLabel,
+  hasActiveGenerationStatus,
 } from '@/lib/display'
 
 const props = defineProps<{
@@ -124,6 +125,7 @@ const displayMarkdown = computed(() => streamMarkdown.value || detail.value?.mar
 const generateMeta = computed(() =>
   getGenerateStatusMeta(streamStatus.value || detail.value?.generate_status),
 )
+const displayGenerateStatus = computed(() => streamStatus.value || detail.value?.generate_status)
 const sourceArticleTitle = computed(() => detail.value?.source_title?.trim() || '')
 const sourceArticleURL = computed(() => detail.value?.source_url?.trim() || '')
 
@@ -170,13 +172,13 @@ watch(
 watch(
   [() => props.open, () => props.articleId, () => detail.value?.generate_status],
   ([open, articleId, generateStatus], _prev, onCleanup) => {
-    if (!open || !articleId || streamFeatureEnabled || generateStatus !== 'generating') {
+    if (!open || !articleId || !hasActiveGenerationStatus(generateStatus)) {
       return
     }
 
     const timer = window.setInterval(() => {
       void refreshArticleData()
-    }, 2000)
+    }, streamFeatureEnabled ? 5000 : 2000)
 
     onCleanup(() => {
       window.clearInterval(timer)
@@ -326,6 +328,14 @@ async function copyPublishLink(record: PublishRecord): Promise<void> {
         </a-descriptions>
       </section>
 
+      <a-alert
+        v-if="displayGenerateStatus === 'failed' && detail.generation_error_message"
+        class="article-drawer__alert"
+        type="error"
+        show-icon
+        :message="detail.generation_error_message"
+      />
+
       <a-tabs v-model:activeKey="activeTab" class="article-drawer__tabs">
         <a-tab-pane key="content" :tab="t('article.preview')">
           <div v-if="displayMarkdown" class="article-drawer__content">

apps/admin-web/src/components/ArticleGenerateStatus.vue

@@ -2,16 +2,14 @@
 import { LoadingOutlined } from '@ant-design/icons-vue'
 import { computed } from 'vue'
 
-import { getGenerateStatusMeta } from '@/lib/display'
+import { getGenerateStatusMeta, hasActiveGenerationStatus } from '@/lib/display'
 
 const props = defineProps<{
   status?: string | null
 }>()
 
 const statusMeta = computed(() => getGenerateStatusMeta(props.status))
-const isLoading = computed(
-  () => props.status === 'queued' || props.status === 'generating' || props.status === 'running',
-)
+const isLoading = computed(() => hasActiveGenerationStatus(props.status))
 </script>
 
 <template>