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

apps/domain/src/lib.rs

@@ -57,6 +57,7 @@ pub use error::DomainError;
 // Agent module top-level items (TurnEvent, SessionRuntime, etc.)
 pub use agent::*;
 // Sub-module items need explicit re-exports
+pub use agent::defaults::*;
 pub use agent::progress::AgentProgress;
 pub use agent::prompt::{compaction_prompt, main_agent_prompt, subagent_directive};
 pub use workflow::*;