Feat: add isOther to question returned by request user input tool (#9890)

### Summary
Add `isOther` to question object from request_user_input tool input and
remove `other` option from the tool prompt to better handle tool input.

codex-rs/protocol/src/request_user_input.rs

@@ -16,6 +16,10 @@ pub struct RequestUserInputQuestion {
     pub id: String,
     pub header: String,
     pub question: String,
+    #[serde(rename = "isOther", default)]
+    #[schemars(rename = "isOther")]
+    #[ts(rename = "isOther")]
+    pub is_other: bool,
     #[serde(skip_serializing_if = "Option::is_none")]
     pub options: Option<Vec<RequestUserInputQuestionOption>>,
 }