fix: 添加文件覆盖保护避免去重冲突

skills/bilibili-analyzer/scripts/prepare.cs

@@ -393,15 +393,19 @@ async Task DeduplicateFramesAsync(string imagesDir, double threshold)
         {
             // Use temp name to avoid conflicts
             var tempName = Path.Combine(imagesDir, $"temp_{i + 1:D4}.jpg");
+            // Delete temp file first if exists
+            if (File.Exists(tempName)) File.Delete(tempName);
             File.Move(remainingFiles[i], tempName);
         }
     }
 
-    // Rename temp files to final names
+    // Rename temp files to final names (with overwrite support)
     var tempFiles = Directory.GetFiles(imagesDir, "temp_*.jpg").OrderBy(f => f).ToList();
     for (int i = 0; i < tempFiles.Count; i++)
     {
         var finalName = Path.Combine(imagesDir, $"frame_{i + 1:D4}.jpg");
+        // Delete final file first if exists (fix: overwrite existing file)
+        if (File.Exists(finalName)) File.Delete(finalName);
         File.Move(tempFiles[i], finalName);
     }