Add item streaming events (#5546)

Adds AgentMessageContentDelta, ReasoningContentDelta,
ReasoningRawContentDelta item streaming events while maintaining
compatibility for old events.

---------

Co-authored-by: Owen Lin <owen@openai.com>

codex-rs/core/src/util.rs

@@ -2,6 +2,7 @@ use std::time::Duration;
 
 use rand::Rng;
 use tracing::debug;
+use tracing::error;
 
 const INITIAL_DELAY_MS: u64 = 200;
 const BACKOFF_FACTOR: f64 = 2.0;
@@ -13,6 +14,14 @@ pub(crate) fn backoff(attempt: u64) -> Duration {
     Duration::from_millis((base as f64 * jitter) as u64)
 }
 
+pub(crate) fn error_or_panic(message: String) {
+    if cfg!(debug_assertions) || env!("CARGO_PKG_VERSION").contains("alpha") {
+        panic!("{message}");
+    } else {
+        error!("{message}");
+    }
+}
+
 pub(crate) fn try_parse_error_message(text: &str) -> String {
     debug!("Parsing server error response: {}", text);
     let json = serde_json::from_str::<serde_json::Value>(text).unwrap_or_default();