feat(core) RequestRule (#9489)

## Summary
Instead of trying to derive the prefix_rule for a command mechanically,
let's let the model decide for us.

## Testing
- [x] tested locally

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

@@ -1754,6 +1754,16 @@ async fn approving_execpolicy_amendment_persists_policy_and_skips_future_prompts
         .await?;
     wait_for_completion(&test).await;
 
+    let developer_messages = first_results
+        .single_request()
+        .message_input_texts("developer");
+    assert!(
+        developer_messages
+            .iter()
+            .any(|message| message.contains(r#"["touch", "allow-prefix.txt"]"#)),
+        "expected developer message documenting saved rule, got: {developer_messages:?}"
+    );
+
     let policy_path = test.home.path().join("rules").join("default.rules");
     let policy_contents = fs::read_to_string(&policy_path)?;
     assert!(