Fix pre-turn compaction context handling and remote compact edge cases

codex-rs/app-server/tests/suite/v2/compaction.rs

@@ -199,15 +199,10 @@ async fn auto_compaction_remote_emits_started_and_completed_items() -> Result<()
 }
 
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
-async fn thread_compact_start_triggers_compaction_and_returns_empty_response() -> Result<()> {
+async fn thread_compact_start_without_history_emits_started_and_completed_items() -> Result<()> {
     skip_if_no_network!(Ok(()));
 
     let server = responses::start_mock_server().await;
-    let sse = responses::sse(vec![
-        responses::ev_assistant_message("m1", "MANUAL_COMPACT_SUMMARY"),
-        responses::ev_completed_with_tokens("r1", 200),
-    ]);
-    responses::mount_sse_sequence(&server, vec![sse]).await;
 
     let codex_home = TempDir::new()?;
     write_mock_responses_config_toml(