fix(front-submit): let drafts save with partial content

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

src/Core/FrontSubmitSave.php

@@ -65,11 +65,16 @@ trait FrontSubmitSave {
         $content = (string) ($data['post_content'] ?? $data['content'] ?? '');
         $excerpt = sanitize_textarea_field((string) ($data['excerpt'] ?? $data['post_excerpt'] ?? ''));
 
-        if ($title === '') {
-            return ['success' => false, 'message' => __('请填写文章标题', 'jio')];
-        }
-        if (trim(wp_strip_all_tags($content)) === '') {
-            return ['success' => false, 'message' => __('还未填写任何内容', 'jio')];
+        // 草稿只要有任何可保存的内容就落库；正式投稿才要求标题与正文齐备。
+        if (!$is_draft) {
+            if ($title === '') {
+                return ['success' => false, 'message' => __('请填写文章标题', 'jio')];
+            }
+            if (trim(wp_strip_all_tags($content)) === '') {
+                return ['success' => false, 'message' => __('还未填写任何内容', 'jio')];
+            }
+        } elseif ($title === '' && trim(wp_strip_all_tags($content)) === '') {
+            return ['success' => false, 'message' => __('请先写点什么再保存', 'jio')];
         }
 
         $categories = $this->normalize_category_ids($data);