More story fixes

SVSim.Database/Repositories/Story/IStoryMasterRepository.cs

@@ -16,4 +16,12 @@ public interface IStoryMasterRepository
 
     Task<StoryChapter?> GetChapterByIdAsync(int storyId);
     Task<SpecialBattleSetting?> GetSbsByIdAsync(int sbsId);
+
+    /// <summary>
+    /// Resolve a wire story_id to a sub-chapter row when no top-level <see cref="StoryChapter"/>
+    /// exists for it. Sub-chapter story_ids have no chapter master data of their own — they're
+    /// progress markers hanging off the parent. Used by /finish to record progress at the sub's
+    /// story_id when the client sends sub-chapter ids directly.
+    /// </summary>
+    Task<StorySubChapter?> FindSubChapterByStoryIdAsync(int storyId);
 }