More story fixes

SVSim.EmulatedEntrypoint/Models/Dtos/Story/InfoDtos.cs

@@ -171,6 +171,38 @@ public class StoryMasterEntry
     [JsonPropertyName("is_skip_enabled")]
     [Key("is_skip_enabled")]
     public bool IsSkipEnabled { get; set; }
+
+    // Optional — prod omits the key entirely on chapters without sub-chapters. Only emitted for
+    // chapters that split into N narrative vignettes (e.g. section 9 ch.13 has 5 sub-chapters).
+    // The client uses each sub's is_finish flag to derive the parent's ChapterClearStatus
+    // (AllCleared / AlreadyRead / NotCleared per StoryChapterData.GetClearStatusUsingSubChapter).
+    // Explicit WhenWritingNull (rather than relying on global policy) so the key is dropped
+    // under any serializer config — including the wire-shape snapshot test which sets
+    // DefaultIgnoreCondition=Never to exercise every populated field.
+    [JsonPropertyName("sub_chapters")]
+    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
+    [Key("sub_chapters")]
+    public List<SubChapterDto>? SubChapters { get; set; }
+}
+
+[MessagePackObject]
+public class SubChapterDto
+{
+    [JsonPropertyName("story_id")]
+    [Key("story_id")]
+    public int StoryId { get; set; }
+
+    [JsonPropertyName("sub_chapter_id")]
+    [Key("sub_chapter_id")]
+    public int SubChapterId { get; set; }
+
+    [JsonPropertyName("is_finish")]
+    [Key("is_finish")]
+    public bool IsFinish { get; set; }
+
+    [JsonPropertyName("is_maintenance_chapter")]
+    [Key("is_maintenance_chapter")]
+    public bool IsMaintenanceChapter { get; set; }
 }
 
 [MessagePackObject]