fix: add a hopefully-temporary sleep to reduce test flakiness (#7848)

Let's see if this `sleep()` call is good enough to fix the test
flakiness we currently see in CI. It will take me some time to upstream
a proper fix, and I would prefer not to disable this test in the
interim.

codex-rs/exec-server/tests/suite/accept_elicitation.rs

@@ -3,6 +3,7 @@ use std::borrow::Cow;
 use std::path::PathBuf;
 use std::sync::Arc;
 use std::sync::Mutex;
+use std::time::Duration;
 
 use anyhow::Context;
 use anyhow::Result;
@@ -82,6 +83,18 @@ prefix_rule(
     };
     notify_readable_sandbox(&project_root_path, codex_linux_sandbox_exe, &service).await?;
 
+    // TODO(mbolin): Remove this hack to remove flakiness when possible.
+    // As noted in the commentary on https://github.com/openai/codex/pull/7832,
+    // an rmcp server does not process messages serially: it takes messages off
+    // the queue and immediately dispatches them to handlers, which may complete
+    // out of order. The proper fix is to replace our custom notification with a
+    // custom request where we wait for the response before proceeding. However,
+    // rmcp does not currently support custom requests, so as a temporary
+    // workaround we just wait a bit to increase the probability the server has
+    // processed the notification. Assuming we can upstream rmcp support for
+    // custom requests, we will remove this once the functionality is available.
+    tokio::time::sleep(Duration::from_secs(4)).await;
+
     // Call the shell tool and verify that an elicitation was created and
     // auto-approved.
     let CallToolResult {