refactor(admin): drop AI connection config page for WP AI Connectors

Remove the "AI 连接配置" page under 扩展&增强 together with the theme's
own OpenAI-compatible provider path. AI generation (SEO, summary, tags)
now runs solely on the WordPress AI Client (wp_ai_client_prompt), with
connections configured through WordPress AI Connectors.

- AI.php keeps only the WP AI Client path: no provider config storage,
  no theme fallback, no rate limiting
- Drop /ai/status, /ai/settings and legacy /ai/seo-suggest routes plus
  their handlers
- Remove dead compat code: AISEO::suggest, AIPrompt::build_seo_prompt
  and the front-submit AI assist flow (its buttons were never rendered
  and its endpoints were never registered)
- Update SEO schema/meta-box guidance that pointed at the deleted page
- Add ai-config-removal contract test and refresh the toast and
  user-features contracts affected by the cleanup

src/Ai/AISEO.php

@@ -107,67 +107,6 @@ class AISEO {
         ];
     }
 
-    /**
-     * 草稿场景：用传入 title/content 生成（兼容旧 /ai/seo-suggest）。
-     */
-    public function suggest(string $title, string $content = ''): array {
-        if (!$this->is_enabled()) {
-            return ['success' => false, 'message' => __('AI SEO 功能未启用', 'aksrt')];
-        }
-
-        if (!class_exists('AKSRT\\Ai\\AI') || !class_exists('AKSRT\\Ai\\AIPrompt')) {
-            return ['success' => false, 'message' => __('AI 模块未加载', 'aksrt')];
-        }
-
-        $ai = AI::get_instance();
-        if (!$ai->is_available()) {
-            return ['success' => false, 'message' => __('AI 服务未启用', 'aksrt')];
-        }
-
-        $title   = trim($title);
-        $content = trim(wp_strip_all_tags($content));
-        if ($title === '' && $content === '') {
-            return [
-                'success' => false,
-                'message' => __('无可用内容，请先填写标题或正文', 'aksrt'),
-            ];
-        }
-
-        $parts = [];
-        if ($title !== '') {
-            $parts[] = '标题: ' . $title;
-        }
-        if ($content !== '') {
-            $content = wp_trim_words($content, 1500, '');
-            $parts[] = "正文:\n" . $content;
-        }
-        $context = implode("\n\n", $parts);
-        $prompt  = AIPrompt::get_instance();
-
-        $title_out = $this->run_field($ai, $context, $prompt->get_seo_title_system_instruction(), 'title');
-        $kw_out    = $this->run_field($ai, $context, $prompt->get_seo_keywords_system_instruction(), 'keywords');
-        $desc_out  = $this->run_field($ai, $context, $prompt->get_seo_description_system_instruction(), 'description');
-
-        $keywords = [];
-        if (!empty($kw_out['content'])) {
-            $keywords = array_values(array_filter(array_map('trim', explode(',', $kw_out['content']))));
-        }
-
-        return [
-            'success' => true,
-            'data'    => [
-                'suggested_title'       => (string) ($title_out['content'] ?? ''),
-                'suggested_description' => (string) ($desc_out['content'] ?? ''),
-                'suggested_keywords'    => $keywords,
-                'fields'                => [
-                    'title'       => $title_out,
-                    'keywords'    => $kw_out,
-                    'description' => $desc_out,
-                ],
-            ],
-        ];
-    }
-
     /**
      * @return string|\WP_Error
      */