Refresh step world state for all sessions (#33665)

## Why

Changes to the selected working directory can select different `AGENTS.md`
instructions. These updates need to reach the model even when the deferred
executor feature is disabled.

## What changed

- Refresh environment readiness and `AGENTS.md` before capturing each step.
- Record model-visible world-state changes for every session instead of gating
  them on the deferred executor feature.
- Preserve the initial environment context without duplicating it.

## Testing

- Cover `AGENTS.md` replacement after a working-directory change.
- Verify that initial environment context remains unique with the deferred
  executor both enabled and disabled.

GitOrigin-RevId: ea5dbe590cc049170259e7eccb6a3346fb2ed8e6

codex-rs/core/src/session/turn.rs

@@ -259,15 +259,9 @@ pub(crate) async fn run_turn(
             )
             .await?;
 
-            if turn_context
-                .config
-                .features
-                .enabled(Feature::DeferredExecutor)
-            {
-                world_state = sess
-                    .record_step_world_state_if_changed(&world_state, step_context.as_ref())
-                    .await;
-            }
+            world_state = sess
+                .record_step_world_state_if_changed(&world_state, step_context.as_ref())
+                .await;
 
             // Construct the input that we will send to the model.
             let sampling_request_input: Vec<ResponseItem> = async {