Separate TUI preferences from server configuration (#42202)

## Why

TUI preferences and persistence paths belong to the local client, while thread
configuration and account requirements may come from the active app server.
Keeping both in the same resolved `Config` can replace live local preferences
when a thread is resumed, forked, reconnected, or switched.

## What changed

- Add `LocalSettings` as the TUI-owned source for UI, history, notice, and local
  persistence settings, and preserve it across session lifecycle transitions.
- Write preference changes to the selected user config file and reload local
  settings from disk when changing roots.
- Use the app server's account response for authentication-dependent onboarding
  and status UI instead of the local model-provider configuration.
- Retain platform family and OS metadata reported by remote app servers.

## Testing

- Cover local setting defaults, overrides, persistence destinations, reloads,
  and preservation across widget replacement and root switching.
- Cover remote platform metadata and server-controlled authentication UI.

GitOrigin-RevId: dbc2965fb1d6cbecb3f973f6133f3dcd4467b753

codex-rs/tui/src/thread_transcript.rs

@@ -48,6 +48,7 @@ pub(crate) async fn load_session_transcript(
             /*turn_cursor*/ None,
             /*item_cursor*/ None,
             /*config*/ None,
+            /*local_settings*/ None,
             HistoryHydrationScope::Complete,
         )
         .await