[core] Allow resume after client errors (#2053)

## Summary
Allow tui conversations to resume after the client fails out of retries.
I tested this with exec / mocked api failures as well, and it appears to
be fine. But happy to add an exec integration test as well!

## Testing
- [x] Added integration test
- [x] Tested locally

codex-rs/core/tests/common/lib.rs

@@ -73,15 +73,26 @@ pub fn load_sse_fixture_with_id(path: impl AsRef<std::path::Path>, id: &str) ->
 
 pub async fn wait_for_event<F>(
     codex: &codex_core::Codex,
-    mut predicate: F,
+    predicate: F,
 ) -> codex_core::protocol::EventMsg
 where
     F: FnMut(&codex_core::protocol::EventMsg) -> bool,
 {
     use tokio::time::Duration;
+    wait_for_event_with_timeout(codex, predicate, Duration::from_secs(1)).await
+}
+
+pub async fn wait_for_event_with_timeout<F>(
+    codex: &codex_core::Codex,
+    mut predicate: F,
+    wait_time: tokio::time::Duration,
+) -> codex_core::protocol::EventMsg
+where
+    F: FnMut(&codex_core::protocol::EventMsg) -> bool,
+{
     use tokio::time::timeout;
     loop {
-        let ev = timeout(Duration::from_secs(1), codex.next_event())
+        let ev = timeout(wait_time, codex.next_event())
             .await
             .expect("timeout waiting for event")
             .expect("stream ended unexpectedly");