Support changing reasoning effort (#2435)

https://github.com/user-attachments/assets/50198ee8-5915-47a3-bb71-69af65add1ef

Building up on #2431 #2428

codex-rs/protocol/src/config_types.rs

@@ -1,10 +1,13 @@
 use serde::Deserialize;
 use serde::Serialize;
 use strum_macros::Display;
+use strum_macros::EnumIter;
 use ts_rs::TS;
 
 /// See https://platform.openai.com/docs/guides/reasoning?api-mode=responses#get-started-with-reasoning
-#[derive(Debug, Serialize, Deserialize, Default, Clone, Copy, PartialEq, Eq, Display, TS)]
+#[derive(
+    Debug, Serialize, Deserialize, Default, Clone, Copy, PartialEq, Eq, Display, TS, EnumIter,
+)]
 #[serde(rename_all = "lowercase")]
 #[strum(serialize_all = "lowercase")]
 pub enum ReasoningEffort {
@@ -13,8 +16,6 @@ pub enum ReasoningEffort {
     #[default]
     Medium,
     High,
-    /// Option to disable reasoning.
-    None,
 }
 
 /// A summary of the reasoning performed by the model. This can be useful for