Add dev message upon review out (#3758)

Proposal: We want to record a dev message like so:

```
{
      "type": "message",
      "role": "user",
      "content": [
        {
          "type": "input_text",
          "text": "<user_action>
  <context>User initiated a review task. Here's the full review output from reviewer model. User may select one or more comments to resolve.</context>
  <action>review</action>
  <results>
  {findings_str}
  </results>
</user_action>"
        }
      ]
    },
```

Without showing in the chat transcript.

Rough idea, but it fixes issue where the user finishes a review thread,
and asks the parent "fix the rest of the review issues" thinking that
the parent knows about it.

### Question: Why not a tool call?

Because the agent didn't make the call, it was a human. + we haven't
implemented sub-agents yet, and we'll need to think about the way we
represent these human-led tool calls for the agent.

codex-rs/core/src/lib.rs

@@ -46,6 +46,7 @@ pub use model_provider_info::built_in_model_providers;
 pub use model_provider_info::create_oss_provider_with_base_url;
 mod conversation_manager;
 mod event_mapping;
+pub mod review_format;
 pub use codex_protocol::protocol::InitialHistory;
 pub use conversation_manager::ConversationManager;
 pub use conversation_manager::NewConversation;