Remove instruction hack for /review (#4896)

We use to put the review prompt in the first user message as well to
bypass statsig overrides, but now that's been resolved and instructions
are being respected, so we're duplicating the review instructions.

Author: dedrisian-oai

codex-rs/core/src/codex.rs

@@ -1586,7 +1586,7 @@ async fn spawn_review_thread(
 
     // Seed the child task with the review prompt as the initial user message.
     let input: Vec<InputItem> = vec![InputItem::Text {
-        text: format!("{base_instructions}\n\n---\n\nNow, here's your task: {review_prompt}"),
+        text: review_prompt,
     }];
     let tc = Arc::new(review_turn_context);
 

codex-rs/core/tests/suite/review.rs

@@ -445,7 +445,7 @@ async fn review_input_isolated_from_parent_history() {
     .await;
     let _complete = wait_for_event(&codex, |ev| matches!(ev, EventMsg::TaskComplete(_))).await;
 
-    // Assert the request `input` contains the environment context followed by the review prompt.
+    // Assert the request `input` contains the environment context followed by the user review prompt.
     let request = &server.received_requests().await.unwrap()[0];
     let body = request.body_json::<serde_json::Value>().unwrap();
     let input = body["input"].as_array().expect("input array");
@@ -473,9 +473,14 @@ async fn review_input_isolated_from_parent_history() {
     assert_eq!(review_msg["role"].as_str().unwrap(), "user");
     assert_eq!(
         review_msg["content"][0]["text"].as_str().unwrap(),
-        format!("{REVIEW_PROMPT}\n\n---\n\nNow, here's your task: Please review only this",)
+        review_prompt,
+        "user message should only contain the raw review prompt"
     );
 
+    // Ensure the REVIEW_PROMPT rubric is sent via instructions.
+    let instructions = body["instructions"].as_str().expect("instructions string");
+    assert_eq!(instructions, REVIEW_PROMPT);
+
     // Also verify that a user interruption note was recorded in the rollout.
     codex.submit(Op::GetPath).await.unwrap();
     let history_event =