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/Cargo.toml

@@ -29,6 +29,7 @@ reqwest = { version = "0.12", features = ["json", "stream"] }
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"
 thiserror = "2.0.12"
+time = { version = "0.3", features = ["formatting", "macros"] }
 tokio = { version = "1", features = [
     "io-std",
     "macros",
@@ -41,6 +42,7 @@ toml = "0.8.20"
 tracing = { version = "0.1.41", features = ["log"] }
 tree-sitter = "0.25.3"
 tree-sitter-bash = "0.23.3"
+uuid = { version = "1", features = ["v4"] }
 
 [target.'cfg(target_os = "linux")'.dependencies]
 libc = "0.2.172"