Add step-scoped data to extension contributors (#34525)

## What changed

- Add an `ExtensionData` store to each `StepContext`.
- Pass the step store to context, world-state, turn-input, and tool contributors so extensions can use capabilities bound to the current sampling step.
- Preserve the captured step context when rebuilding initial context during compaction.

GitOrigin-RevId: 51f3105d3a793f60534f122f9be8247c131c2ca5

codex-rs/core/src/compact_remote_v2.rs

@@ -283,17 +283,13 @@ async fn run_remote_compact_task_inner_impl(
         build_v2_compacted_history(&prompt_input, compaction_output);
     analytics_details.retained_image_count = Some(retained_images);
     let (new_window_number, new_window_ids) = sess.advance_auto_compact_window().await;
-    let (new_history, world_state_baseline) = process_compacted_history(
-        sess.as_ref(),
-        compaction_turn_context.as_ref(),
-        compacted_history,
-        &initial_context_injection,
-    )
-    .await;
+    let (new_history, world_state_baseline) =
+        process_compacted_history(sess.as_ref(), compacted_history, &initial_context_injection)
+            .await;
 
     let reference_context_item = match initial_context_injection {
         InitialContextInjection::DoNotInject => None,
-        InitialContextInjection::BeforeLastUserMessage(_) => {
+        InitialContextInjection::BeforeLastUserMessage { .. } => {
             Some(compaction_turn_context.to_turn_context_item())
         }
     };