feat: save session transcripts when using Rust CLI (#845)

This adds support for saving transcripts when using the Rust CLI. Like
the TypeScript CLI, it saves the transcript to `~/.codex/sessions`,
though it uses JSONL for the file format (and `.jsonl` for the file
extension) so that even if Codex crashes, what was written to the
`.jsonl` file should generally still be valid JSONL content.

codex-rs/core/src/lib.rs

@@ -20,6 +20,7 @@ pub mod mcp_server_config;
 mod mcp_tool_call;
 mod models;
 pub mod protocol;
+mod rollout;
 mod safety;
 mod user_notification;
 pub mod util;