Stabilize Bazel test timing under load

codex-rs/app-server/BUILD.bazel

@@ -6,6 +6,7 @@ codex_rust_crate(
     integration_test_tags_extra_by_stem = {
         "all": ["flaky"],
     },
+    integration_test_args = ["--test-threads=4"],
     integration_test_timeout = "long",
     test_tags = ["no-sandbox"],
 )

codex-rs/core/src/tools/handlers/multi_agents_tests.rs

@@ -182,7 +182,7 @@ async fn wait_for_redirected_envelope_in_history(
     thread: &Arc<CodexThread>,
     expected: &InterAgentCommunication,
 ) {
-    timeout(Duration::from_secs(5), async {
+    timeout(Duration::from_secs(30), async {
         loop {
             let history_items = thread
                 .codex