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/runtime.rs

@@ -361,18 +361,14 @@ impl MemoryStartupContext {
         agent: SpawnedConsolidationAgent,
     ) -> anyhow::Result<()> {
         let SpawnedConsolidationAgent { thread_id, thread } = agent;
-        let thread = self
-            .thread_manager
-            .remove_thread(&thread_id)
-            .await
-            .unwrap_or(thread);
-
         tokio::time::timeout(Duration::from_secs(10), thread.shutdown_and_wait())
             .await
             .map_err(|_| {
                 anyhow::anyhow!("memory consolidation agent {thread_id} shutdown timed out")
             })??;
 
+        self.thread_manager.remove_thread(&thread_id).await;
+
         Ok(())
     }
 }