fix(widgets): restore single-card reference UI for search and quote widgets

The 搜索框 and 一言 sidebar widgets fell into the generic renderer branch, so
they rendered a .jio-panel card wrapping a second bespoke card
(.jio-widget-search / .jio-widget-quote). In-article 一言 also used
divergent modifier classes and an extra hover rule.

- search: render through the shared jio_get_search_box() (legacy keyword,
  history and category pickers) inside one reference card, mirroring the
  reference widget's markup and title default 「搜索」
- quote: render the reference .yiyan-box card itself as the click root; the
  shell now emits only the reference widget-container/title wrapper
- article 一言: adopt the reference class lists for header, footer and the
  standalone after-article box; drop the invented yiyan--* modifiers and
  the duplicate hover/opacity rules
- client: fill .cn/.en in the reference order (first line .cn, second .en)
  and drop the stale window.JioYiyan bridge plus the dead qv-yiyan.php AJAX
  path in runtime main.js
- schema: replace the ad-hoc search_style radio with the reference switches
  (keywords, history, input category, more_cats) and default title
- assets: enqueue assets/js/yiyan.js through the quote widget's asset list

Tests: widget-system suite 820/821 (the one failure is the pre-existing
frontend-lifecycle theme-init stub); new search/quote card contracts pass.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

assets/css/frontend/single-post/hidden-content.css

@@ -1,45 +1,3 @@
-/* ---- Yiyan inline blocks (single post) ---- */
-.yiyan--header,
-.yiyan--footer {
-    margin: 16px 0;
-    padding: 12px 16px;
-}
-
-.yiyan--box {
-    margin: 24px 0;
-    padding: 20px;
-    border-radius: 8px;
-    background: var(--card-bg, #fff);
-    box-shadow: var(--card-shadow, 0 2px 8px rgba(0, 0, 0, .06));
-}
-
-.jio-yiyan[data-jio-yiyan] {
-    cursor: pointer;
-    transition: box-shadow .2s ease, opacity .2s ease;
-}
-
-.jio-yiyan[data-jio-yiyan]:hover,
-.jio-yiyan[data-jio-yiyan]:focus-visible {
-    box-shadow: inset 0 0 5px 0 var(--focus-shadow-color, rgba(253, 83, 161, .3));
-}
-
-.jio-yiyan .yiyan {
-    line-height: 1.8;
-}
-
-.jio-yiyan .yiyan .en {
-    font-size: .9em;
-    opacity: .8;
-}
-
-.jio-yiyan.is-loading {
-    opacity: .65;
-}
-
-.jio-yiyan.is-error .cn {
-    color: var(--muted-color, #777);
-}
-
 /* ---- Front / After content insertion ---- */
 .article-front-content,
 .article-after-content {