refactor(package): replace manual MB calculation with format function

- Replace round() calculation with formatMegabytes() function call
- Add new formatMegabytes() utility function for consistent formatting
- Use number_format() for precise decimal handling in MB conversion
- Centralize byte to MB conversion logic in single reusable function

package.php

@@ -501,7 +501,7 @@ echo "[8/8] 清理临时文件...\n";
 
 // 获取文件大小
 $packageSize = filesize($outputFile);
-$packageSizeMB = round($packageSize / 1024 / 1024, 2);
+$packageSizeMB = formatMegabytes($packageSize);
 
 echo "临时目录: {$topLevelDir}\n";
 removeDirectory($topLevelDir);
@@ -742,10 +742,15 @@ function packageUnixLike(): void
     }
     $cleanupArchive = false;
 
-    $sizeMb = round(filesize($outputFile) / 1024 / 1024, 2);
+    $sizeMb = formatMegabytes(filesize($outputFile));
     echo "Package successful: {$outputFile} ({$sizeMb} MB)\n";
 }
 
+function formatMegabytes(int $bytes): string
+{
+    return number_format($bytes / 1024 / 1024, 3, '.', '');
+}
+
 /**
  * 递归复制目录
  * @param string $src 源目录