Add skill approval event/response (#12633)

Set the stage for skill-level permission approval in addition to
command-level.

Behind a feature flag.

codex-rs/exec/src/event_processor_with_human_output.rs

@@ -811,7 +811,8 @@ impl EventProcessor for EventProcessorWithHumanOutput {
             | EventMsg::RealtimeConversationStarted(_)
             | EventMsg::RealtimeConversationRealtime(_)
             | EventMsg::RealtimeConversationClosed(_)
-            | EventMsg::DynamicToolCallRequest(_) => {}
+            | EventMsg::DynamicToolCallRequest(_)
+            | EventMsg::SkillRequestApproval(_) => {}
         }
         CodexStatus::Running
     }