docs: correct 0.4.0 theme platform wording

CHANGELOG.md

@@ -38,8 +38,8 @@ Every release entry is provided in English and Simplified Chinese.
 
 - **A more consistent interface** — spacing now follows a 4px rhythm, while type sizes, row heights, icon buttons, corners, borders, shadows, animations, and control states share the same visual rules across the app.
   **中文：** 界面的间距现在统一按 4px 节奏排布，字号、行高、图标按钮、圆角、描边、阴影、动画和各种操作状态也都使用同一套视觉规则，页面之间看起来更整齐、更一致。
-- **Themes can follow the system** — enable “Follow system light/dark mode” in Appearance and Nebula will switch between the matching light and dark themes when Windows or macOS changes. Choosing a theme card manually turns automatic switching off, so an explicit choice is never overwritten.
-  **中文：** 主题现在可以跟着系统明暗模式自动切换啦。在“外观”里打开“跟随系统明暗模式”后，Nebula 会随 Windows 或 macOS 切换到同系列的浅色或深色主题；手动点选主题卡会退出自动跟随，不会覆盖用户明确选择的主题。
+- **Themes can follow the system** — Appearance now includes “Follow system light/dark mode”. Nebula switches between the matching light and dark themes while preserving the selected theme family. Choosing a theme card manually turns automatic switching off, so an explicit choice is never overwritten.
+  **中文：** 新增跟随系统明暗模式。在“外观”里开启后，Nebula 会切换到同系列的浅色或深色主题，同时保留用户选择的主题系列；手动点选主题卡会退出自动跟随，不会覆盖用户明确选择的主题。
 - **Text boxes behave the same everywhere** — renaming tabs, filtering files, entering Git commit messages, editing SSH hosts, and searching commands now all support the same copy, paste, select-all, replacement, IME, and selection behavior.
   **中文：** 各处输入框终于用起来一致了：无论是重命名标签页、筛选文件、填写 Git 提交信息、编辑 SSH 主机还是搜索命令，都能用同样的复制、粘贴、全选、替换和中文输入法操作。
 - **A calmer sidebar** — `TABS` and `SSH HOSTS` now have clearer heading sizes, weights, and shades. The two `+` buttons only appear when the pointer is over their section title, the tab menu uses a vertical three-dot icon, and the empty SSH message is easier to read.