[codex][app-server] introduce codex/event/raw_item events (#5578)

codex-rs/app-server-protocol/src/protocol.rs

@@ -717,6 +717,8 @@ pub struct SendUserMessageResponse {}
 #[serde(rename_all = "camelCase")]
 pub struct AddConversationListenerParams {
     pub conversation_id: ConversationId,
+    #[serde(default)]
+    pub experimental_raw_events: bool,
 }
 
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, JsonSchema, TS)]