[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/compact.rs

@@ -31,6 +31,7 @@ use codex_protocol::protocol::EventMsg;
 use codex_protocol::protocol::TurnStartedEvent;
 use codex_protocol::protocol::WarningEvent;
 use codex_protocol::user_input::UserInput;
+use codex_rollout_trace::InferenceTraceContext;
 use codex_utils_output_truncation::TruncationPolicy;
 use codex_utils_output_truncation::approx_token_count;
 use codex_utils_output_truncation::truncate_text;
@@ -546,6 +547,9 @@ async fn drain_to_completed(
             turn_context.reasoning_summary,
             turn_context.config.service_tier,
             turn_metadata_header,
+            // Rollout tracing currently models remote compaction only; local compaction streams
+            // are left untraced until the reducer has a first-class local compaction lifecycle.
+            &InferenceTraceContext::disabled(),
         )
         .await?;
     loop {