Wait for memory consolidation shutdown before finishing jobs (#36140)

## Why

A phase-two memory job could release its lease while its consolidation agent was
still shutting down, allowing another worker to race the existing agent.

## What changed

- Await consolidation-agent shutdown before validating artifacts and completing
  the job.
- Keep the lease until it expires if shutdown fails, and remove the agent from
  the thread manager only after shutdown succeeds.

## Testing

Update startup tests to wait for the phase-two job lifecycle to finish and verify
that the consolidation thread has been removed.

GitOrigin-RevId: 7ac3a7369529822ac95fd2ee9dcb27d39c191d20

codex-rs/memories/write/src/phase2.rs

@@ -406,6 +406,17 @@ mod agent {
             {
                 emit_token_usage_metrics(context.as_ref(), &token_usage);
             }
+
+            if let Err(err) = context
+                .shutdown_consolidation_agent(SpawnedConsolidationAgent { thread_id, thread })
+                .await
+            {
+                warn!("failed to auto-close global memory consolidation agent {thread_id}: {err}");
+                // Keep the existing lease until it expires so another worker cannot race a
+                // consolidation agent whose shutdown has not completed.
+                return;
+            }
+
             let artifacts_valid = if agent_completed {
                 match validate_consolidation_artifacts(&memory_root).await {
                     Ok(()) => true,
@@ -469,18 +480,6 @@ mod agent {
             } else if !agent_completed {
                 job::failed(context.as_ref(), &db, &claim, "failed_agent").await;
             }
-
-            let cleanup_context = Arc::clone(&context);
-            tokio::spawn(async move {
-                if let Err(err) = cleanup_context
-                    .shutdown_consolidation_agent(SpawnedConsolidationAgent { thread_id, thread })
-                    .await
-                {
-                    warn!(
-                        "failed to auto-close global memory consolidation agent {thread_id}: {err}"
-                    );
-                }
-            });
         });
     }