chore(branding): remove leftover upstream theme identifiers

The theme was renamed Zibll/子比 → AKSRT → Jio, but upstream branding
survived the sweeps in CSS classes, the SVG sprite prefix, a persisted
widget field ID, JS events, admin Vue class names, test infrastructure
and docblocks.

Renames:
- zib-widget / zib-widget-wrap / zib-slider → jio-widget-box /
  jio-widget-box-wrap / jio-slider-box (jio-widget is taken by the modern
  widget shell, jio-box-* by the card primitives)
- zib-partners-scroll + zps-* → jio-partners-scroll + jps-*
- zib-combo-info-card + zci-* → jio-combo-info-card + jci-*
- zibsvg- → jiosvg-, including the exported picker helpers and the
  fa-zibsvg- family-prefix guard
- zibpay_type → pay_type; the dual-read fallback in PostQuery collapses
  to a single key
- [zibajax="submit"] dropped (no PHP emitter); zib_ajax.success →
  jio_ajax.success
- aks-* admin Vue classes → jio-*
- zib_palette() → palette()

User-facing vendor traces are gone: the floating "more" button default no
longer ships a zibll.com link or 子比主题 marketing copy, the notice
widget ships no preset promo entries, and the four 官网教程 links are
removed from the post-list admin schema.

Test infrastructure renamed to neutral names (docker-compose.reference.yml,
Caddyfile, article-baseline.json, modern-widgets-contract.test.cjs) with
their DB/volume/env/slug identifiers following.

Kept intentionally, documented in tests/fixtures/README.md: the golden
fixture reference fingerprint (a SHA-256 record of an external directory,
read by validate-widget-golden / generate-widget-golden-fixture /
audit-widget-system), the doesNotMatch guards that prove the old tokens are
gone, and the reference theme's own meta key in the visual fixtures.

No backward-compat or data migration: saved widget configs holding old
icon keys or the old field ID silently lose them, per the project's
rewrite-over-compatibility rule.

Verified: 132/132 node contract tests, php tests/widget-system/run.php
(146 assertions), audit-admin-contracts, audit-psr4-paths and
validate-widget-golden all green; tracked bundles regenerated and in sync.

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

inc/helpers/posts-renderer/markup.php

@@ -210,13 +210,13 @@ if (!function_exists('jio_render_mini_list')) {
 
 if (!function_exists('jio_render_placeholder')) {
 	/**
-	 * 骨架屏占位，1:1 对齐参考主题 `zib_get_post_placeholder()`。
+	 * 骨架屏占位。
 	 *
 	 * 骨架块复用真实卡片的 posts-item / post-graphic / item-body 结构与尺寸，
 	 * 只是把内容换成 .placeholder。列表模式四行（标题 t1、摘要 k1、k2、两枚 s1），
 	 * 卡片模式三行（标题 t1、摘要 k2、两枚 s1）。
 	 *
-	 * 刻意与真实条目不同的两点（均与参考主题一致）：
+	 * 刻意与真实条目不同的两点：
 	 * - **不写 `ajax-item`**：否则 `find('.ajax-item')` / ajax-list 的 `inject()`
 	 *   会把骨架当成真实条目删除或定位。
 	 * - **元素是 `<div>` 而非 `<posts>`**，且 card 分支的缩略图是