fix: 手动停止录制时跳过耗时的文件分析，避免 save dialog 延迟/卡住

fragmented MP4 在 SIGINT 后可能导致 ffprobe/ffmpeg 分析卡住。
stopRequested 时直接返回基本文件信息，不跑 ffprobe 和音量检测。

Sources/StreamRecorderKit/FFmpegRecorder.swift

@@ -135,6 +135,25 @@ public final class FFmpegRecorder: StreamRecorderEngine {
             throw RecordingError.outputNotFound
         }
         
+        // 如果是手动停止，跳过耗时的分析（fragmented MP4 可能导致 ffprobe 卡住）
+        if stopRequested {
+            NSLog("[Recorder] Stop requested, skipping analysis")
+            let attrs = try? FileManager.default.attributesOfItem(atPath: outputPath)
+            let fileSize = attrs?[.size] as? Int64 ?? 0
+            let result = RecordingResult(
+                outputPath: outputPath,
+                duration: duration,
+                fileSize: fileSize,
+                hasVideo: true,
+                hasAudio: true,
+                videoInfo: nil,
+                audioInfo: nil,
+                audioLevel: nil
+            )
+            delegate?.recorder(self, didFinishWithResult: result)
+            return
+        }
+        
         NSLog("[Recorder] Analyzing output file...")
         // 分析输出文件
         let ffprobePath = ffmpegPath.replacingOccurrences(of: "ffmpeg", with: "ffprobe")