feat: centralize default constants and refactor overlay enter handling in TUI

apps/interfaces/tui/src/run.rs

@@ -30,6 +30,9 @@ use crate::view;
 /// save settings.
 #[tracing::instrument]
 pub fn run_single_process() -> Result<()> {
+    let rt = tokio::runtime::Runtime::new()?;
+    let _guard = rt.enter();
+
     // Create session state
     info!("starting single-process TUI");
     let (_store, mut state) = create_local_session()?;