feat: include reasoning_effort in NewConversationResponse (#3506)

`ClientRequest::NewConversation` picks up the reasoning level from the user's defaults in `config.toml`, so it should be reported in `NewConversationResponse`.

codex-rs/mcp-server/src/codex_message_processor.rs

@@ -593,6 +593,7 @@ impl CodexMessageProcessor {
                 let response = NewConversationResponse {
                     conversation_id,
                     model: session_configured.model,
+                    reasoning_effort: session_configured.reasoning_effort,
                     rollout_path: session_configured.rollout_path,
                 };
                 self.outgoing.send_response(request_id, response).await;

codex-rs/mcp-server/src/outgoing_message.rs

@@ -258,6 +258,7 @@ pub(crate) struct OutgoingError {
 mod tests {
     use codex_core::protocol::EventMsg;
     use codex_core::protocol::SessionConfiguredEvent;
+    use codex_protocol::config_types::ReasoningEffort;
     use codex_protocol::mcp_protocol::ConversationId;
     use codex_protocol::mcp_protocol::LoginChatGptCompleteNotification;
     use pretty_assertions::assert_eq;
@@ -279,6 +280,7 @@ mod tests {
             msg: EventMsg::SessionConfigured(SessionConfiguredEvent {
                 session_id: conversation_id,
                 model: "gpt-4o".to_string(),
+                reasoning_effort: ReasoningEffort::default(),
                 history_log_id: 1,
                 history_entry_count: 1000,
                 initial_messages: None,
@@ -312,6 +314,7 @@ mod tests {
         let session_configured_event = SessionConfiguredEvent {
             session_id: conversation_id,
             model: "gpt-4o".to_string(),
+            reasoning_effort: ReasoningEffort::default(),
             history_log_id: 1,
             history_entry_count: 1000,
             initial_messages: None,
@@ -342,6 +345,7 @@ mod tests {
             "msg": {
                 "session_id": session_configured_event.session_id,
                 "model": session_configured_event.model,
+                "reasoning_effort": session_configured_event.reasoning_effort,
                 "history_log_id": session_configured_event.history_log_id,
                 "history_entry_count": session_configured_event.history_entry_count,
                 "type": "session_configured",

codex-rs/mcp-server/tests/suite/codex_message_processor_flow.rs

@@ -90,6 +90,7 @@ async fn test_codex_jsonrpc_conversation_flow() {
     let NewConversationResponse {
         conversation_id,
         model,
+        reasoning_effort: _,
         rollout_path: _,
     } = new_conv_resp;
     assert_eq!(model, "mock-model");

codex-rs/mcp-server/tests/suite/create_conversation.rs

@@ -59,6 +59,7 @@ async fn test_conversation_create_and_send_message_ok() {
     let NewConversationResponse {
         conversation_id,
         model,
+        reasoning_effort: _,
         rollout_path: _,
     } = to_response::<NewConversationResponse>(new_conv_resp)
         .expect("deserialize newConversation response");