[codex-analytics] add protocol-native turn timestamps (#16638)

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[//]: # (BEGIN SAPLING FOOTER)
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with [ReviewStack](https://reviewstack.dev/openai/codex/pull/16638).
* #16870
* #16706
* #16659
* #16641
* #16640
* __->__ #16638

codex-rs/core/tests/suite/resume_warning.rs

@@ -53,6 +53,7 @@ fn resume_history(
         history: vec![
             RolloutItem::EventMsg(EventMsg::TurnStarted(TurnStartedEvent {
                 turn_id: turn_id.clone(),
+                started_at: None,
                 model_context_window: None,
                 collaboration_mode_kind: ModeKind::Default,
             })),
@@ -66,6 +67,8 @@ fn resume_history(
             RolloutItem::EventMsg(EventMsg::TurnComplete(TurnCompleteEvent {
                 turn_id,
                 last_agent_message: None,
+                completed_at: None,
+                duration_ms: None,
             })),
         ],
         rollout_path: rollout_path.to_path_buf(),