Improve Guardian report diagnostics (#42033)

## Why

Reports from a large thread tree can exceed the rollout attachment limit, making
the threads involved in a failed Guardian review harder to diagnose.

## What changed

- Prioritize descendants with retained failed reviews when selecting bounded
  report rollouts, while always preserving the reported thread.
- Include each selected thread's available Guardian trunk rollout alongside its
  conversation rollout.
- Add a thread index attachment with selected filenames, bounded omission details,
  retained failure threads, and the process-wide discarded-record count.
- Link failed-review records to their reviewed turn and target item when available.

## Testing

- Cover failed-review prioritization, bounded omission metadata, discarded-record
  accounting, and turn/item linkage in Guardian report records.

GitOrigin-RevId: ae7916c27a3c279e899cd5a6ead8a4b7e0cc26a1

codex-rs/core/src/guardian/feedback.rs

@@ -3,6 +3,8 @@
 
 use super::GuardianAssessmentOutcome;
 use super::approval_request::format_guardian_action_pretty;
+use super::approval_request::guardian_request_target_item_id;
+use super::approval_request::guardian_request_turn_id;
 use super::prompt::parse_guardian_assessment;
 use super::review_session::GuardianReviewSessionOutcome;
 use super::review_session::GuardianReviewSessionParams;
@@ -20,6 +22,7 @@ const MAX_RECORD_BYTES: usize = 4 * 1024 * 1024;
 struct ReviewFeedbackRecord<'a> {
     reviewed_thread_id: ThreadId,
     reviewed_turn_id: &'a str,
+    target_item_id: Option<&'a str>,
     reviewer_thread_id: ThreadId,
     model: &'a str,
     status: &'a str,
@@ -64,7 +67,11 @@ pub(super) async fn record_failed_review(
     let history = reviewer.clone_history().await;
     ReviewFeedbackRecord {
         reviewed_thread_id: params.parent_session.thread_id(),
-        reviewed_turn_id: &params.parent_context.turn().sub_id,
+        reviewed_turn_id: guardian_request_turn_id(
+            &params.request,
+            &params.parent_context.turn().sub_id,
+        ),
+        target_item_id: guardian_request_target_item_id(&params.request),
         reviewer_thread_id: reviewer.thread_id(),
         model: &params.model,
         status,

codex-rs/core/src/guardian/feedback_tests.rs

@@ -11,6 +11,7 @@ fn oversized_context_keeps_the_action_and_decision() -> anyhow::Result<()> {
     ReviewFeedbackRecord {
         reviewed_thread_id: thread_id,
         reviewed_turn_id: "parent-turn",
+        target_item_id: Some("push-call"),
         reviewer_thread_id,
         model: "review-model",
         status: "denied",
@@ -22,7 +23,8 @@ fn oversized_context_keeps_the_action_and_decision() -> anyhow::Result<()> {
         context_omitted: false,
     }
     .store();
-    let contents = codex_feedback::guardian_review_failures_attachment(&[thread_id])
+    let contents = codex_feedback::guardian_review_failures(&[thread_id])
+        .attachment
         .expect("failed-review record")
         .buffer;
     assert_eq!(
@@ -30,6 +32,7 @@ fn oversized_context_keeps_the_action_and_decision() -> anyhow::Result<()> {
         json!({
             "reviewed_thread_id": thread_id,
             "reviewed_turn_id": "parent-turn",
+            "target_item_id": "push-call",
             "reviewer_thread_id": reviewer_thread_id,
             "model": "review-model",
             "status": "denied",

codex-rs/core/src/guardian/tests.rs

@@ -3619,11 +3619,15 @@ async fn guardian_ephemeral_retry_preserves_parallel_trunk_and_fork_history() ->
             .send(())
             .expect("second guardian review gate should still be open");
         assert_eq!(second_review.await?, ReviewDecision::Approved);
-        let feedback = codex_feedback::guardian_review_failures_attachment(&[session.thread_id()])
+        let feedback = codex_feedback::guardian_review_failures(&[session.thread_id()])
+            .attachment
             .expect("failed ephemeral review survives cleanup and subsequent allowed reviews");
         let record: serde_json::Value = serde_json::from_slice(&feedback.buffer)?;
         assert_eq!(
             serde_json::json!({
+                "reviewed_thread_id": record["reviewed_thread_id"],
+                "reviewed_turn_id": record["reviewed_turn_id"],
+                "target_item_id": record["target_item_id"],
                 "reviewer_thread_id": record["reviewer_thread_id"],
                 "status": record["status"],
                 "decision": record["decision"],
@@ -3632,6 +3636,9 @@ async fn guardian_ephemeral_retry_preserves_parallel_trunk_and_fork_history() ->
                 )?["command"],
             }),
             serde_json::json!({
+                "reviewed_thread_id": session.thread_id(),
+                "reviewed_turn_id": turn.sub_id,
+                "target_item_id": "shell-guardian-3",
                 "reviewer_thread_id": failed_ephemeral_request_body["client_metadata"]["thread_id"],
                 "status": "invalid_decision",
                 "decision": "not valid guardian json",