Add recovery guidance to content-filter retries (#49119)

## Why

Responses stopped by `content_filter` previously followed generic stream-error retry handling without guidance about the block. Retried requests need instructions to explain the limitation and offer a permitted alternative.

## What changed

- Recognize content-filter failures as a distinct error while preserving retryability and the existing public error representation.
- Append developer guidance to the conversation after each sampling block, retaining delivered output and using the existing retry handling.
- Support a model catalog override through `model_messages.content_filter_guidance`. Missing, null, blank, or values exceeding 512 UTF-8 bytes fall back to bundled guidance.
- The bundled guidance tells the model to avoid reproducing or working around blocked content, briefly explain the limitation, offer a permitted alternative, and continue unrelated authorized work.

## Testing

Add a scenario and request-history snapshot covering repeated blocks, catalog guidance on each retry, retained partial output, and eventual completion. Add error-mapping assertions for retryability, public error classification, and error text.

GitOrigin-RevId: ba0c201b3a5a3acf5cfa971332027240e0690225

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

@@ -11,6 +11,7 @@ use crate::compact::InitialContextInjection;
 use crate::compact::run_inline_auto_compact_task;
 use crate::compact_remote_v2::run_inline_remote_auto_compact_task as run_inline_remote_auto_compact_task_v2;
 use crate::connectors;
+use crate::context::ContentFilterGuidance;
 use crate::context::ContextualUserFragment;
 use crate::context::UserVerificationNotice;
 use crate::environment_selection::TurnEnvironmentSnapshot;
@@ -1697,15 +1698,33 @@ async fn run_sampling_request(
 
         let original_input = original_input.get_or_insert(prompt.input);
 
-        let retry = handle_response_stream_error(
-            &mut retry_state,
-            max_retries,
-            err,
-            client_session,
-            &sess,
-            &turn_context,
-            ResponsesStreamRequest::Sampling,
-        )
+        let retry = async {
+            if matches!(err.details(), CodexErrorDetails::ContentFilter) {
+                let model_info = &step_context.settings.model_info;
+                let guidance = ContentFilterGuidance {
+                    text: codex_prompts::ResolvedModelMessages::from_model(model_info)
+                        .content_filter_guidance()
+                        .to_string(),
+                };
+                sess.record_conversation_items(
+                    &turn_context,
+                    model_info,
+                    &[ContextualUserFragment::into(guidance)],
+                )
+                .await;
+            }
+
+            handle_response_stream_error(
+                &mut retry_state,
+                max_retries,
+                err,
+                client_session,
+                &sess,
+                &turn_context,
+                ResponsesStreamRequest::Sampling,
+            )
+            .await
+        }
         .or_cancel(&preempt)
         .or_cancel(&cancellation_token)
         .await?;