Rescue chat completion changes (#1846)

https://github.com/openai/codex/pull/1835 has some messed up history.

This adds support for streaming chat completions, which is useful for ollama. We should probably take a very skeptical eye to the code introduced in this PR.

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Co-authored-by: Ahmed Ibrahim <aibrahim@openai.com>

codex-rs/core/src/client_common.rs

@@ -72,6 +72,7 @@ pub enum ResponseEvent {
     },
     OutputTextDelta(String),
     ReasoningSummaryDelta(String),
+    ReasoningContentDelta(String),
 }
 
 #[derive(Debug, Serialize)]