同步上游 zip：合并任务后台化 + 合并整剧可直接播放；保留 ultrafast+4线程 转码优化与 .gitignore 本地规则

internal/app/ui_playback.go

@@ -51,6 +51,7 @@ type playbackSession struct {
 }
 
 type playbackEpisode struct {
+	Merged    bool   `json:"merged,omitempty"`
 	VIP       bool   `json:"vip,omitempty"`
 	Index     int    `json:"index"`
 	Episode   string `json:"episode"`
@@ -190,15 +191,22 @@ func (app *UIApp) handlePlaybackOpen(writer http.ResponseWriter, request *http.R
 	var collectionErr error
 	app.mu.Lock()
 	if input.FromHistory && previous.Mode == "collection" && downloadAllowed(request.Context()) {
-		candidate := app.tasks[previous.TaskID]
-		if isPlayableDownloadTask(candidate) && candidate.DramaID == previous.DramaID {
-			input.TaskID = candidate.ID
-		} else {
-			for _, taskID := range app.taskOrder {
-				candidate = app.tasks[taskID]
-				if isPlayableDownloadTask(candidate) && candidate.DramaID == previous.DramaID {
-					input.TaskID = candidate.ID
-					break
+		if strings.HasPrefix(previous.TaskID, mergedPlaybackPrefix) && previous.TaskID == mergedPlaybackPrefix+previous.DramaID {
+			if _, _, err := app.mergedPlaybackTaskLocked(previous.TaskID); err == nil {
+				input.TaskID = previous.TaskID
+			}
+		}
+		if input.TaskID == "" {
+			candidate := app.tasks[previous.TaskID]
+			if isPlayableDownloadTask(candidate) && candidate.DramaID == previous.DramaID {
+				input.TaskID = candidate.ID
+			} else {
+				for _, taskID := range app.taskOrder {
+					candidate = app.tasks[taskID]
+					if isPlayableDownloadTask(candidate) && candidate.DramaID == previous.DramaID {
+						input.TaskID = candidate.ID
+						break
+					}
 				}
 			}
 		}
@@ -310,6 +318,10 @@ func (app *UIApp) handlePlaybackOpen(writer http.ResponseWriter, request *http.R
 		_, _, episode.Danmaku = hongguoPlaybackIDs(task)
 		if len(downloadIDs) > 0 {
 			episode.TaskID = downloadIDs[index]
+			episode.Merged = strings.HasPrefix(episode.TaskID, mergedPlaybackPrefix)
+			if episode.Merged {
+				episode.Danmaku = false
+			}
 		}
 		episodes = append(episodes, episode)
 	}