refactor(search): 只展示 keyword 续接词,去掉 titles 段

产品决定:搜索建议只展示 ts_stat 高频词续接(如'美'→美国/美军/美国政府),
不要真实文章 id 提示(用户认为这种'文章#566871'是噪音,没连续性)。

改动:
- SearchSuggestionsResponse 去 title,只剩 query + keywords
- SearchService 只查 search_keywords,fallback 路径也只针对 keywords
- Feed.vue: 删掉 suggestTitles 状态 + SuggestTitleOption 类型联合,
  renderSuggestion 简化成 '词' 标签 + 词文本 + 右侧 weight 数字
- 0011 迁移: 删 search_title_suggestions 表 + 3 索引 + trigger + 函数
  (trigger 在每篇文章 INSERT/UPDATE 都会跑,删了能省掉无用性能损耗)
- 删除: app/models/search_title_suggestion.py + backfill_search_suggestions.py
  替换成: app/scripts/refresh_search_keywords.py(只跑一次词频刷新)

frontend/src/views/Feed.vue

@@ -6,7 +6,7 @@ import {
   NPagination, NAutoComplete, useMessage,
 } from 'naive-ui'
 import { articlesApi, readsApi, sourcesApi, type ArticleListItem, type Source } from '@/api/articles'
-import { searchApi, type SearchKeyword, type SearchTitleSuggestion } from '@/api/search'
+import { searchApi, type SearchKeyword } from '@/api/search'
 import { useDebounce } from '@/composables/useDebounce'
 import { useAuthStore } from '@/stores/auth'
 import dayjs from 'dayjs'
@@ -37,18 +37,16 @@ const hideRead = ref(true)
 
 const sourceOptions = ref<{ label: string; value: string }[]>([])
 
-// === 搜索建议(autocomplete) ===
+// === 搜索建议(autocomplete) — 纯 keyword 续接词 ===
 // 触发:q 变化(用户输入)→ 250ms debounce → 调 /api/v1/search/suggestions
 // 取消:每次新输入前 abort 上一次未完成的请求,避免旧响应覆盖新结果
 // 选词:@select → 填入 q + 触发搜索(不再等回车)
-const suggestTitles = ref<SearchTitleSuggestion[]>([])
 const suggestKeywords = ref<SearchKeyword[]>([])
 let suggestAbort: AbortController | null = null
 
 async function fetchSuggestions(prefix: string) {
   const p = prefix.trim()
   if (!p) {
-    suggestTitles.value = []
     suggestKeywords.value = []
     return
   }
@@ -58,9 +56,8 @@ async function fetchSuggestions(prefix: string) {
   suggestAbort = ctrl
   try {
     const resp = await searchApi.suggestions(p, 10, { signal: ctrl.signal })
-    // 注意:race condition 防护 — 只采纳最新请求的响应
+    // race condition 防护 — 只采纳最新请求的响应
     if (suggestAbort === ctrl) {
-      suggestTitles.value = resp.titles
       suggestKeywords.value = resp.keywords
     }
   } catch (e: any) {
@@ -70,7 +67,6 @@ async function fetchSuggestions(prefix: string) {
       // eslint-disable-next-line no-console
       console.debug('search suggestions failed:', e?.message)
       if (suggestAbort === ctrl) {
-        suggestTitles.value = []
         suggestKeywords.value = []
       }
     }
@@ -84,78 +80,42 @@ watch(q, (v) => {
 })
 
 // === NAutoComplete options ===
-// 把 titles + keywords 拼成扁平 options 数组。
-// 用 discriminated union 让 TypeScript 在 onSelect 里能自动 narrow 出 meta 的具体类型。
-type SuggestTitleOption = {
+// 只用 keyword 续接词,扁平结构。
+type SuggestOption = {
   label: string
   value: string
-  type: 'title'
-  meta: SearchTitleSuggestion
-}
-type SuggestKeywordOption = {
-  label: string
-  value: string
-  type: 'keyword'
   meta: SearchKeyword
 }
-type SuggestOption = SuggestTitleOption | SuggestKeywordOption
 
 const suggestOptions = computed<SuggestOption[]>(() => {
-  const out: SuggestOption[] = []
-  for (const t of suggestTitles.value) {
-    // 标题项:label 用 #id 标识(可后续扩展拉标题),value 是 id 字符串
-    out.push({
-      label: `#${t.id}`,
-      value: t.id.toString(),
-      type: 'title',
-      meta: t,
-    })
-  }
-  for (const k of suggestKeywords.value) {
-    out.push({
-      label: k.word,
-      value: k.word,
-      type: 'keyword',
-      meta: k,
-    })
-  }
-  return out
+  return suggestKeywords.value.map((k) => ({
+    label: k.word,
+    value: k.word,
+    meta: k,
+  }))
 })
 
-// 自定义 render:显示分类图标 + 类型
+// 自定义 render:显示"词"标签 + 词文本 + 权重
 function renderSuggestion(opt: SuggestOption) {
   return h(
     'div',
     { class: 'feed-suggest-row' },
     [
-      h('span', { class: `feed-suggest-tag feed-suggest-tag-${opt.type}` },
-        opt.type === 'title' ? '文章' : '词'),
+      h('span', { class: 'feed-suggest-tag feed-suggest-tag-keyword' }, '词'),
       h('span', { class: 'feed-suggest-text' }, opt.label),
+      h('span', { class: 'feed-suggest-weight' }, String(opt.meta.weight)),
     ],
   )
 }
 
-// 选完候选词:从当前 suggestOptions 反查 meta。
-// naive-ui 的 NAutoComplete 选完时只把 value 写回 v-model,我们额外用
-// ref 维护一个 lastSelectedType,模板里在 click 时先 setType,on-select 时
-// 再读 — 但更简单的做法:看 value 格式。title 类型的 value 是纯数字 id 字符串,
-// keyword 类型是中文/字母词。
+// 选完候选词:naive-ui 把 value 写回 v-model,我们从 suggestOptions 找 meta
 function onSelectSuggestion(value: string) {
-  // 反查 suggestOptions 找 meta
   const matched = suggestOptions.value.find((o) => o.value === value)
-  if (matched?.type === 'title') {
-    router.push(`/article/${matched.meta.id}`)
-    return
-  }
-  if (matched?.type === 'keyword') {
+  if (matched) {
     q.value = matched.meta.word
     resetToFirstPage()
-    return
-  }
-  // 兜底
-  if (/^\d+$/.test(value)) {
-    router.push(`/article/${value}`)
   } else {
+    // 兜底:value 就是用户要的关键词
     q.value = value
     resetToFirstPage()
   }
@@ -762,10 +722,6 @@ onMounted(async () => {
   line-height: 1.4;
   flex-shrink: 0;
 }
-.feed-suggest-tag-title {
-  background: #dbeafe;
-  color: #1e40af;
-}
 .feed-suggest-tag-keyword {
   background: #f3e8ff;
   color: #6b21a8;
@@ -777,6 +733,12 @@ onMounted(async () => {
   flex: 1;
   min-width: 0;
 }
+.feed-suggest-weight {
+  flex-shrink: 0;
+  font-size: 11px;
+  color: #94a3b8;
+  font-variant-numeric: tabular-nums;
+}
 
 /* ===== 移动端(<= 768px):过滤条全宽,允许换行 ===== */
 @media (max-width: 768px) {