• Redesign the base package downloader with a clearer package list, corrected download size totals, and direct base package folder selection.
• Improve base package download reliability by downloading selected packages sequentially, reusing aria2c safely, recovering from incompatible resume data, and fixing cancellation and retry issues.
• Correctly detect and support downgrading to an older base package version.
• Restore the previous base package selection after disabling the X-Plane 12 original base package.

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• 重新设计底包下载页面，优化底包列表与操作布局，修正下载总量统计，并支持直接选择底包目录。
• 提升底包下载稳定性：所选底包改为顺序安装，安全复用 aria2c，自动处理不兼容的断点数据，并修复取消和重试异常。
• 正确识别并支持将底包降级到旧版本。
• 关闭 X-Plane 12 原始底包后，恢复此前的普通底包启用状态。