diag: add stop-time tracks check to detect HLS variant switching

Sources/PlayerRecorder.swift

@@ -582,6 +582,36 @@ final class PlayerRecorder: NSObject {
               statsSnapshot.videoFrames, statsSnapshot.processCallCount, statsSnapshot.appendCount,
               statsSnapshot.peakAmplitude, statsSnapshot.activeCallCount, statsSnapshot.silentCallCount)
         
+        // 诊断：检查录制结束时 tracks 是否变化
+        if let pi = currentPlayerItem, let boundID = tapContext?.mixTrackID {
+            let currentTracks = pi.tracks
+            NSLog("[Recorder:DIAG] Stop-time tracks: count=%d", currentTracks.count)
+            var stopLog = "\n=== Stop-time tracks check ===\n"
+            stopLog += "Bound trackID: \(boundID)\n"
+            stopLog += "Current tracks count: \(currentTracks.count)\n"
+            var foundBoundTrack = false
+            for (i, t) in currentTracks.enumerated() {
+                let tid = t.assetTrack?.trackID ?? -1
+                let mtype = t.assetTrack?.mediaType.rawValue ?? "?"
+                NSLog("[Recorder:DIAG]   stopTrack[%d]: trackID=%d mediaType=%@ enabled=%d", i, tid, mtype, t.isEnabled)
+                stopLog += "  track[\(i)]: trackID=\(tid) mediaType=\(mtype) enabled=\(t.isEnabled)\n"
+                if tid == boundID {
+                    foundBoundTrack = true
+                }
+            }
+            stopLog += "Bound trackID \(boundID) still exists: \(foundBoundTrack)\n"
+            NSLog("[Recorder:DIAG] Bound trackID=%d still exists: %d", boundID, foundBoundTrack)
+            // 追加到日志文件
+            if let moviesDir = FileManager.default.urls(for: .moviesDirectory, in: .userDomainMask).first {
+                let logPath = moviesDir.appendingPathComponent("MiniPlayer/tap_install_log.txt")
+                if let handle = try? FileHandle(forWritingTo: logPath) {
+                    handle.seekToEndOfFile()
+                    handle.write(stopLog.data(using: .utf8)!)
+                    handle.closeFile()
+                }
+            }
+        }
+        
         currentPlayerItem = nil
         
         videoInput?.markAsFinished()