test(config): round-trip follow-system fields; docs + comment fixes from review

docs/features.md

@@ -19,6 +19,7 @@
 - **Command palette** <kbd>⌘ P</kbd> · scrollback search <kbd>⌘ F</kbd>
 - **⌘-click links** · desktop notifications · copy on select (opt-in, Settings → Terminal → Clipboard)
 - **Eight themes, plus your own** — YAML seed themes with solid, gradient, or image backgrounds; iTerm2 `.itermcolors` import; in-app color editor with a background-image picker
+- **Sync with system** — Settings → Appearance; pick separate light and dark themes and tty7 follows the OS appearance live (`theme_follow_system`, `theme_preset_light` / `theme_preset_dark` in `config.json`)
 - **Window opacity & blur** — Settings → Appearance → Window; applies to every theme, *Follow theme* returns to the theme's own `opacity` / `blur`
 - **CJK / IME input**
 

docs/features.zh-CN.md

@@ -19,6 +19,7 @@
 - **命令面板** <kbd>⌘ P</kbd> · 回滚搜索 <kbd>⌘ F</kbd>
 - **⌘ 点击打开链接** · 桌面通知 · 划选即复制（可选，设置 → 终端 → 剪贴板）
 - **8 套主题，也能自定义** — YAML 种子主题，背景支持纯色、渐变或图片；可导入 iTerm2 `.itermcolors`；应用内颜色编辑器带背景图选择
+- **跟随系统外观** — 设置 → Appearance；分别选好浅色和深色主题，tty7 随系统深浅模式实时切换（`config.json` 中的 `theme_follow_system`、`theme_preset_light` / `theme_preset_dark`）
 - **窗口透明与模糊** — 设置 → Appearance → Window；对所有主题生效，*Follow theme* 恢复主题自带的 `opacity` / `blur`
 - **CJK / 输入法输入**
 

src/core/config.rs

@@ -851,6 +851,27 @@ mod tests {
         assert_eq!(back.ssh_profile_frecency.get(&id).unwrap().count, 4);
     }
 
+    #[test]
+    fn theme_follow_system_defaults_and_round_trips() {
+        // Old configs (no follow-system keys) must land on off + the built-in
+        // light/dark pair, so nothing changes until the user opts in.
+        let cfg: Config = serde_json::from_str(r#"{"theme_preset":"dracula"}"#).unwrap();
+        assert!(!cfg.theme_follow_system);
+        assert_eq!(cfg.theme_preset_light, "light");
+        assert_eq!(cfg.theme_preset_dark, "dark");
+        assert_eq!(cfg.theme_preset, "dracula");
+
+        let mut cfg = Config::default();
+        cfg.theme_follow_system = true;
+        cfg.theme_preset_light = "one_light".to_string();
+        cfg.theme_preset_dark = "dracula".to_string();
+        let json = serde_json::to_string(&cfg).unwrap();
+        let back: Config = serde_json::from_str(&json).unwrap();
+        assert!(back.theme_follow_system);
+        assert_eq!(back.theme_preset_light, "one_light");
+        assert_eq!(back.theme_preset_dark, "dracula");
+    }
+
     #[test]
     fn font_features_are_optional_and_parse_as_gpui_features() {
         let cfg: Config =

src/ui/app.rs

@@ -1137,10 +1137,11 @@ impl Tty7App {
     }
 
     /// Turn "sync with system appearance" on/off (the Appearance switch).
-    /// Flipping it never visibly changes the theme by itself: turning it on
-    /// seeds the slot matching the manual theme's own brightness with that
-    /// theme, and turning it off adopts whatever is on screen as the manual
-    /// choice.
+    /// Turning it off never visibly changes the theme: whatever is on screen
+    /// is adopted as the manual choice. Turning it on seeds the slot matching
+    /// the manual theme's own brightness with that theme — so the look only
+    /// changes when the OS is currently in the *other* mode, where switching
+    /// to that mode's slot is exactly what the feature promises.
     pub(crate) fn set_theme_follow_system(
         &mut self,
         on: bool,

src/ui/settings.rs

@@ -360,8 +360,8 @@ pub(crate) struct SettingsState {
     /// Global window-opacity slider (Appearance's Window section). Shows the
     /// effective value; dragging sets the config override.
     pub(crate) window_opacity_slider: Entity<SliderState>,
-    /// The color editor for the active editable theme, or `None` when the active
-    /// theme is read-only (a built-in / import) or the system is being followed.
+    /// The color editor for the effective (on-screen) theme, or `None` when
+    /// that theme is read-only (a built-in / import).
     pub(crate) theme_editor: Option<ThemeEditor>,
     /// Whether the theme picker panel is open beside the content pane
     /// (Appearance section only). Toggled from the theme card(s).