refactor(ui): remove env overrides for ui settings

Why:
- env toggles for alt-screen and theme were requested to be removed
- keep UI behavior consistent across environments

Impact:
- INTAR_* theme/alt-screen env overrides no longer apply
- Tests: just check

Author: icepuma

crates/intar-ui/src/app.rs

@@ -169,11 +169,7 @@ enum AltScreenMode {
 
 impl AltScreenMode {
     fn from_env() -> Self {
-        if use_alt_screen_from_env() {
-            Self::Enabled
-        } else {
-            Self::Disabled
-        }
+        Self::Enabled
     }
 
     fn enabled(self) -> bool {
@@ -234,7 +230,7 @@ impl App {
         agent_binary_aarch64: Vec<u8>,
     ) -> Self {
         let now = Instant::now();
-        let theme_settings = ThemeSettings::from_env();
+        let theme_settings = ThemeSettings::resolve();
         Self {
             scenario,
             runner: None,
@@ -1058,22 +1054,6 @@ fn restore_terminal(
     Ok(())
 }
 
-fn use_alt_screen_from_env() -> bool {
-    if env_flag("INTAR_NO_ALT_SCREEN") == Some(true) {
-        return false;
-    }
-    env_flag("INTAR_ALT_SCREEN").unwrap_or(true)
-}
-
-fn env_flag(key: &str) -> Option<bool> {
-    let value = std::env::var(key).ok()?;
-    match value.trim().to_ascii_lowercase().as_str() {
-        "1" | "true" | "yes" | "on" => Some(true),
-        "0" | "false" | "no" | "off" => Some(false),
-        _ => None,
-    }
-}
-
 fn detect_arch() -> String {
     #[cfg(target_arch = "x86_64")]
     return "x86_64".to_string();

crates/intar-ui/src/colors.rs

@@ -60,13 +60,6 @@ impl Default for Theme {
 }
 
 impl ThemeSettings {
-    #[must_use]
-    pub fn from_env() -> Self {
-        let color_level = ColorLevel::detect();
-        let mode = ThemeMode::from_env_override().unwrap_or(ThemeMode::Dark);
-        Self { mode, color_level }
-    }
-
     #[must_use]
     pub fn resolve() -> Self {
         let color_level = ColorLevel::detect();
@@ -76,17 +69,8 @@ impl ThemeSettings {
 }
 
 impl ThemeMode {
-    #[must_use]
-    fn from_env_override() -> Option<Self> {
-        env_theme_override("INTAR_THEME").or_else(|| env_theme_override("CLITHEME"))
-    }
-
     #[must_use]
     fn resolve(color_level: ColorLevel) -> Self {
-        if let Some(mode) = Self::from_env_override() {
-            return mode;
-        }
-
         if color_level == ColorLevel::None {
             return ThemeMode::Dark;
         }
@@ -324,15 +308,6 @@ fn palette_light_ansi16() -> ThemePalette {
     }
 }
 
-fn env_theme_override(var: &str) -> Option<ThemeMode> {
-    let value = env::var(var).ok()?;
-    match value.trim().to_ascii_lowercase().as_str() {
-        "dark" => Some(ThemeMode::Dark),
-        "light" => Some(ThemeMode::Light),
-        _ => None,
-    }
-}
-
 fn detect_theme_mode() -> Option<ThemeMode> {
     if !io::stdin().is_tty() || !io::stdout().is_tty() {
         return None;