在 Linux 平台使用 dbus-send 检测深色模式设置

[Glavo]

No description provided.

[Copilot]

Pull request overview

为 Linux 平台增加通过 dbus-send（xdg-desktop-portal Settings API）读取系统 color-scheme，从而在“自动”主题亮度模式下更准确跟随系统深色/浅色设置。

Changes:

• 在 Themes.getDefaultBrightness() 中新增 Linux 分支，通过 dbus-send 调用 org.freedesktop.portal.Settings.Read 获取 org.freedesktop.appearance color-scheme
• 解析返回值并映射到 Brightness.DARK/LIGHT，失败时记录 warning 日志
• 增加相关 imports（Path, FileUtils, LOG）

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[Copilot]

This runs an external process synchronously inside getDefaultBrightness(), which is used by a JavaFX ObjectBinding (computeValue() -> getBrightness()), so it will typically execute on the FX thread. SystemUtils.run(...) can block up to 15s (see HMCLCore/.../SystemUtils.java:98-103), which risks noticeable UI freezes on Linux if dbus-send hangs. Consider enforcing a much shorter overall wait (e.g., Process.waitFor with a small timeout and then destroy the process) or moving the D-Bus query off the FX thread and caching the result before bindings are evaluated.

[Copilot]

trim().split(" ") only splits on single space characters and will behave poorly with other whitespace (tabs/newlines) and with the multi-space indentation dbus-send commonly prints. To make theme detection more robust, split on \\s+ (or parse the trailing integer via a regex) before interpreting the last token as the color-scheme value.

Suggested change

	).trim().split(" ");
	).trim().split("\\s+");