[rollout_trace] Record core session rollout traces (#18877)

## Summary

Wires rollout trace recording into `codex-core` session and turn
execution. This records the core model request/response, compaction, and
session lifecycle boundaries needed for replay without yet tracing every
nested runtime/tool boundary.

## Stack

This is PR 2/5 in the rollout trace stack.

- [#18876](https://github.com/openai/codex/pull/18876): Add rollout
trace crate
- [#18877](https://github.com/openai/codex/pull/18877): Record core
session rollout traces
- [#18878](https://github.com/openai/codex/pull/18878): Trace tool and
code-mode boundaries
- [#18879](https://github.com/openai/codex/pull/18879): Trace sessions
and multi-agent edges
- [#18880](https://github.com/openai/codex/pull/18880): Add debug trace
reduction command

## Review Notes

This layer is the first live integration point. The important review
question is whether trace recording is isolated from normal session
behavior: trace failures should not become user-visible execution
failures, and recording should preserve the existing turn/session
lifecycle semantics.

The PR depends on the reducer/data model from the first stack entry and
only introduces the core recorder surface that later PRs use for richer
runtime and relationship events.

codex-rs/core/src/state/service.rs

@@ -23,6 +23,7 @@ use codex_mcp::McpConnectionManager;
 use codex_models_manager::manager::ModelsManager;
 use codex_otel::SessionTelemetry;
 use codex_rollout::state_db::StateDbHandle;
+use codex_rollout_trace::RolloutTraceRecorder;
 use codex_thread_store::LocalThreadStore;
 use std::path::PathBuf;
 use tokio::sync::Mutex;
@@ -41,6 +42,7 @@ pub(crate) struct SessionServices {
     pub(crate) analytics_events_client: AnalyticsEventsClient,
     pub(crate) hooks: Hooks,
     pub(crate) rollout: Mutex<Option<RolloutRecorder>>,
+    pub(crate) rollout_trace: RolloutTraceRecorder,
     pub(crate) user_shell: Arc<crate::shell::Shell>,
     pub(crate) shell_snapshot_tx: watch::Sender<Option<Arc<crate::shell_snapshot::ShellSnapshot>>>,
     pub(crate) show_raw_agent_reasoning: bool,