Add safety check notification and error handling (#19055)

Adds a new app-server notification that fires when a user account has
been flagged for potential safety reasons.

codex-rs/exec/src/event_processor_with_jsonl_output.rs

@@ -489,6 +489,7 @@ impl EventProcessorWithJsonOutput {
                 }));
                 CodexStatus::Running
             }
+            ServerNotification::ModelVerification(_) => CodexStatus::Running,
             ServerNotification::ThreadTokenUsageUpdated(notification) => {
                 self.last_total_token_usage = Some(notification.token_usage);
                 CodexStatus::Running