Promote Windows Sandbox (#11341)

1. Move Windows Sandbox NUX to right after trust directory screen
2. Don't offer read-only as an option in Sandbox NUX.
Elevated/Legacy/Quit
3. Don't allow new untrusted directories. It's trust or quit
4. move experimental sandbox features to `[windows]
sandbox="elevated|unelevatd"`
5. Copy tweaks = elevated -> default, non-elevated -> non-admin

codex-rs/tui/src/app_event.rs

@@ -212,6 +212,12 @@ pub(crate) enum AppEvent {
         preset: ApprovalPreset,
     },
 
+    /// Begin the non-elevated Windows sandbox setup flow.
+    #[cfg_attr(not(target_os = "windows"), allow(dead_code))]
+    BeginWindowsSandboxLegacySetup {
+        preset: ApprovalPreset,
+    },
+
     /// Enable the Windows sandbox feature and switch to Agent mode.
     #[cfg_attr(not(target_os = "windows"), allow(dead_code))]
     EnableWindowsSandboxForAgentMode {