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.

---------

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

codex-rs/core/src/protocol.rs

@@ -359,6 +359,12 @@ pub enum EventMsg {
     /// Agent reasoning delta event from agent.
     AgentReasoningDelta(AgentReasoningDeltaEvent),
 
+    /// Raw chain-of-thought from agent.
+    AgentReasoningRawContent(AgentReasoningRawContentEvent),
+
+    /// Agent reasoning content delta event from agent.
+    AgentReasoningRawContentDelta(AgentReasoningRawContentDeltaEvent),
+
     /// Ack the client's configure message.
     SessionConfigured(SessionConfiguredEvent),
 
@@ -464,6 +470,16 @@ pub struct AgentReasoningEvent {
     pub text: String,
 }
 
+#[derive(Debug, Clone, Deserialize, Serialize)]
+pub struct AgentReasoningRawContentEvent {
+    pub text: String,
+}
+
+#[derive(Debug, Clone, Deserialize, Serialize)]
+pub struct AgentReasoningRawContentDeltaEvent {
+    pub delta: String,
+}
+
 #[derive(Debug, Clone, Deserialize, Serialize)]
 pub struct AgentReasoningDeltaEvent {
     pub delta: String,