recorder: 新增「BGM 跟随视频剪辑」选项（剪辑策略四条的现状核对）

Source/AutoRecorder.cs

@@ -526,6 +526,7 @@ private static void BeginRun(Level level) {
         // The selected mode is run-wide; rhythm exceptions are attached to individual clips.
         reconstructBgm = MicroblocksQolUtilsModule.Settings.BgmMode == BgmRecordingMode.SfxOnlyWithPostMix;
         recordingRoomName = null;
+        recordingRoomBgmFollowsVideo = MicroblocksQolUtilsModule.Settings.RecordingBgmFollowsVideo;
     }
 
     private static void StartRunRecording(Level level) {
@@ -968,7 +969,8 @@ private static void ObserveRoom(Level level) {
             DeathReplayPrefix.Add(deathClip);
 
         recordingRoomName = room;
-        recordingRoomBgmFollowsVideo = RhythmMapDetector.IsRhythmSensitive(level.Session.MapData, room);
+        recordingRoomBgmFollowsVideo = MicroblocksQolUtilsModule.Settings.RecordingBgmFollowsVideo
+            || RhythmMapDetector.IsRhythmSensitive(level.Session.MapData, room);
         if (branchActive) {
             branchStartSeconds = fullTime;
             branchMusicStart = MusicPosition.Read();

Source/QolSettings.cs

@@ -333,6 +333,13 @@ public AutoRecordingMode AutomaticRecording {
     [DefaultValue(false)]
     public bool RecordingKeepFailedAttempts { get; set; }
 
+    // Rhythm-sensitive rooms already read the real source time so music keeps its
+    // on-screen timing. Outside those rooms the BGM is reconstructed across cuts and
+    // therefore keeps playing while the video jumps; this opt-in asks for the strict
+    // behaviour (jump with the video) in every room.
+    [DefaultValue(false)]
+    public bool RecordingBgmFollowsVideo { get; set; }
+
     [DefaultValue(60)]
     [SettingRange(30, 120)]
     public int RecordingFrameRate { get; set; } = 60;

Source/QolSettingsOverlay.cs

@@ -1680,6 +1680,10 @@ SettingRow Golden(SettingRow row) {
             row.IsVisible = () => settings.AutomaticRecording == AutoRecordingMode.Golden;
             return row;
         }
+        SettingRow BgmRebuildOnly(SettingRow row) {
+            row.IsVisible = () => settings.BgmMode == BgmRecordingMode.SfxOnlyWithPostMix;
+            return row;
+        }
         Group(RecorderSettingsSection.Automatic,
             EnumRow("自动录制", () => settings.AutomaticRecording, value => settings.AutomaticRecording = value),
             Golden(EnumRow("成功时录到", () => settings.GoldenRecordingEnd, value => settings.GoldenRecordingEnd = value)),
@@ -1696,6 +1700,10 @@ SettingRow Golden(SettingRow row) {
             Toggle("切面自动存档（保持视频连续）", () => settings.RecordingAutoSaveOnTransition,
                 value => settings.RecordingAutoSaveOnTransition = value),
             EnumRow("BGM 拼接", () => settings.BgmMode, value => settings.BgmMode = value),
+            // Only the reconstruction mode has a music cursor that can either follow the
+            // source time or keep playing across cuts; game-mix BGM already follows the video.
+            BgmRebuildOnly(Toggle("BGM 跟随视频剪辑", () => settings.RecordingBgmFollowsVideo,
+                value => settings.RecordingBgmFollowsVideo = value)),
             Toggle("剪辑冻结帧", () => settings.RecordingRemoveFreezeFrames, value => settings.RecordingRemoveFreezeFrames = value, highlightWhenOn: true),
             Range("录制帧率", () => settings.RecordingFrameRate, value => settings.RecordingFrameRate = value,
                 30, 120, 30, value => $"{value} FPS"),

Tests/Recorder/Stubs.cs

@@ -77,7 +77,7 @@ public class QolSettings {
         public AutoRecordingMode AutomaticRecording;
         public bool AutoRecorderEnabled => AutomaticRecording != AutoRecordingMode.Off;
         public bool DeathReplayEnabled, RecordingRemoveFreezeFrames, RecordingEditingEnabled = true,
-            RecordingKeepPausedFrames, RecordingKeepFailedAttempts;
+            RecordingKeepPausedFrames, RecordingKeepFailedAttempts, RecordingBgmFollowsVideo;
         public int DeathReplayBufferSeconds=30, RecordingRetentionCount, AutoRecordingRetentionCount, DeathReplayRetentionCount;
         public string RecordingDirectory="";
         public GoldenRecordingEnd GoldenRecordingEnd;

Tests/Recording.Policy/Program.cs

@@ -48,6 +48,25 @@ static void SetField(object owner, string name, object value) => owner.GetType()
 Call("BeginRun", level);
 Check(!State<bool>("reconstructBgm"), "explicit game-mix mode was ignored");
 
+// Forcing "BGM follows the video" makes every room read source time, so clips split by
+// room/music cuts jump with the picture instead of letting the reconstructed BGM run on.
+// The default (false) must keep the automatic per-room policy asserted above.
+settings.BgmMode = BgmRecordingMode.SfxOnlyWithPostMix;
+settings.RecordingBgmFollowsVideo = true;
+session.Level = normal.Name;
+Call("BeginRun", level);
+Check(State<bool>("recordingRoomBgmFollowsVideo"), "forced BGM policy was not applied before the first room snapshot");
+foreach (var room in new[] { normal, sensitive, normal, triggered }) {
+    session.Level = room.Name;
+    Call("ObserveRoom", level);
+    Check(State<bool>("recordingRoomBgmFollowsVideo"), $"forced BGM policy ignored in room {room.Name}");
+}
+settings.RecordingBgmFollowsVideo = false;
+session.Level = normal.Name;
+Call("BeginRun", level);
+Call("ObserveRoom", level);
+Check(!State<bool>("recordingRoomBgmFollowsVideo"), "clearing the forced BGM policy did not restore the per-room policy");
+
 // Exercise actual clip creation for BOTH sinks with a deterministic stopped clock.
 // No native handle, files, hooks, Steam process or game settings are touched.
 object Recording(string path) {